Aromatic isothiocyanates

ABSTRACT

Aromatic isothiocyanates of formula C 
                         
liquid-crystalline media comprising one or more compounds of formula C, and high-frequency components comprising these media, especially microwave components for high-frequency devices, such as devices for shifting the phase of microwaves, tunable filters, tunable metamaterial structures, and electronic beam steering antennas, e.g. phased array antennas.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. national stage application filed and claiming priority under 35 U.S.C. §§ 120 and 365(a) of International Application No. PCT/EP2020/085026, filed Dec. 8, 2020, which claims priority under 35 U.S.C. § 119 of European Patent Application No. 19214643.9, filed Dec. 10, 2019, each of which applications is incorporated herein by reference in its entirety and for all purposes.

FIELD OF THE INVENTION

The present invention relates to aromatic isothiocyanates, liquid-crystalline media comprising same, and to high-frequency components comprising these media, especially microwave components for high-frequency devices, such as devices for shifting the phase of microwaves, tunable filters, tunable metamaterial structures, and electronic beam steering antennas (e.g. phased array antennas), and to devices comprising said components.

BACKGROUND

Liquid-crystalline media have a been used for many years in electro-optical displays (liquid crystal displays: LCDs) in order to display information. More recently, however, liquid-crystalline media have also been proposed for use in components for microwave technology, such as, for example, in DE 10 2004 029 429.1 A and in JP 2005-120208 (A).

A. Gaebler, F. Goelden, S. Müller, A. Penirschke and R. Jakoby “Direct Simulation of Material Permittivities using an Eigen-Susceptibility Formulation of the Vector Variational Approach”, 12MTC 2009—International Instrumentation and Measurement Technology Conference, Singapore, 2009 (IEEE), pp. 463-467, describe the corresponding properties of the known liquid-crystal mixture E7 (Merck KGaA, Germany).

DE 10 2004 029 429 A describes the use of liquid-crystal media in microwave technology, inter alia in phase shifters. Therein, liquid-crystalline media with respect to their properties in the corresponding frequency range have been discussed and liquid-crystalline media based on mixtures of mostly aromatic nitriles and isothiocyanates have been shown.

Fluorine atoms are commonly used in mesogenic compounds to introduce polarity. Especially in combination with a terminal NCS group high dielectric anisotropy values can be achieved.

In EP 2 982 730 A1, mixtures are described that completely consist of isothiocyanate compounds.

SUMMARY

However, compositions available for the use in microwave applications are still afflicted with several disadvantages. It is required to improve these media with respect to their general physical properties, the shelf life and the stability under operation in a device. In view of the multitude of different parameters which have to be considered and improved for the development of liquid crystalline media for microwave application it is desirable to have a broader range of possible mixture components for the development of such liquid-crystalline media.

An object of the present invention is to provide a compound for the use in liquid crystalline media with improved properties relevant for the application in the microwave range of the electromagnetic spectrum.

To solve the problem, a compound of formula C shown below is provided and a liquid crystalline medium comprising the compound.

The present invention relates to a compound of formula C

-   -   in which     -   R^(C) denotes H, alkyl or alkoxy having 1 to 12 C atoms, or         alkenyl, alkenyloxy or alkoxyalkyl having 2 to 12 C atoms, in         which one or more CH₂-groups may be replaced by

-   -    or a group R^(P),     -   R^(P) denotes halogen, CN, NCS, R^(F), R^(F)—O— or R^(F)—S—,         wherein         -   R^(F) denotes fluorinated alkyl or fluorinated alkenyl             having up to 9 C atoms,     -   Z^(C1), Z^(C2) identically or differently, denote —CH═CH—,         —CF═CF—, —CH═CF—, —CF═CH—, —C≡C— or a single bond, preferably         —C≡C— or a single bond,     -   X denotes Cl or F, preferably F,     -   Y denotes H, Cl, F, alkyl or alkoxy each having 1 to 6 C atoms,         preferably, H, F, CH₃ or C₂H₅, very preferably H,     -   t is 0, 1 or 2, preferably 0 or 1, and

-   -    denote a radical selected from the following groups:     -   a) the group consisting of 1,4-phenylene, 1,4-naphthylene, and         2,6-naphthylene, in which one or two CH groups may be replaced         by N and in which one or more H atoms may be replaced by L,     -   b) the group consisting of trans-1,4-cyclohexylene,         1,4-cyclohexenylene, bicyclo[1.1.1]pentane-1,3-diyl,         4,4′-bicyclohexylene, bicyclo[2.2.2]octane-1,4-diyl,         spiro[3.3]heptane-2,6-diyl, in which one or more non-adjacent         CH₂ groups may be replaced by —O— and/or —S— and in which one or         more H atoms may be replaced by F,     -   c) the group consisting of thiophene-2,5-diyl,         thieno[3,2-b]thiophene-2,5-diyl, selenophene-2,5-diyl, each of         which may also be mono- or polysubstituted by L, wherein     -   L on each occurrence, identically or differently, denotes F, Cl,         CN, SCN, SF₅ or straight-chain or branched, in each case         optionally fluorinated, alkyl, alkoxy, alkylcarbonyl,         alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1         to 12 C atoms.

The present invention further relates to a compound of formula N

-   -   in which the occurring groups and parameters have the meanings         given above for formula C.

According to another aspect of the present invention there is provided a process for the synthesis of compounds of formula C from compounds of formula N.

The present invention further relates to a liquid-crystalline medium comprising a compound of formula C and to the use of a liquid-crystalline medium comprising a compound of formula C in a component for high-frequency technology.

According to another aspect of the present invention there is provided a component and a device comprising said component, both operable in the microwave region of the electromagnetic spectrum. Preferred components are phase shifters, varactors, wireless and radio wave antenna arrays, matching circuits and adaptive filters.

Preferred embodiments of the present invention are subject-matter of the dependent claims or can also be taken from the description.

Surprisingly, it has been found that it is possible to achieve liquid-crystalline media having excellent stability and at the same time a high dielectric anisotropy, suitably fast switching times, a suitable, nematic phase range, high tunability and low dielectric loss, by using compounds of formula C in liquid-crystalline media.

The media according to the present invention are distinguished by a high clearing temperature, a broad nematic phase range and excellent low-temperature stability (LTS). As a result, devices containing the media are operable under extreme temperature conditions.

The media are further distinguished by high values of the dielectric anisotropy and low rotational viscosities. As a result, the threshold voltage, i.e. the minimum voltage at which a device is switchable, is very low. A low operating voltage and low threshold voltage is desired in order to enable a device having improved switching characteristics and high energy efficiency. Low rotational viscosities enable fast switching of the devices according to the invention.

These properties as a whole make the media particularly suitable for use in components and devices for high-frequency technology and applications in the microwave range, in particular devices for shifting the phase of microwaves, tunable filters, tunable metamaterial structures, and electronic beam steering antennas (e.g. phased array antennas).

DETAILED DESCRIPTION

Herein, “high-frequency technology” means applications of electromagnetic radiation having frequencies in the range of from 1 MHz to 1 THz, preferably from 1 GHz to 500 GHz, more preferably 2 GHz to 300 GHz, particularly preferably from about 5 GHz to 150 GHz.

As used herein, halogen is F, Cl, Br or I, preferably F or Cl, particularly preferably F.

Herein, alkyl is straight-chain or branched and has 1 to 15 C atoms, is preferably straight-chain and has, unless indicated otherwise, 1, 2, 3, 4, 5, 6 or 7 C atoms and is accordingly preferably methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl or n-heptyl.

Herein, branched alkyl is preferably isopropyl, s-butyl, isobutyl, isopentyl, 2-methylbutyl, 2-methylhexyl or 2-ethylhexyl.

Herein, an alkoxy radical is straight-chain or branched and contains 1 to 15 C atoms. It is preferably straight-chain and has, unless indicated otherwise, 1, 2, 3, 4, 5, 6 or 7 C atoms and is accordingly preferably methoxy, ethoxy, n-propoxy, n-butoxy, n-pentoxy, n-hexoxy or n-heptoxy.

Herein, an alkenyl radical is preferably an alkenyl radical having 2 to 15 C atoms, which is straight-chain or branched and contains at least one C—C double bond. It is preferably straight-chain and has 2 to 7 C atoms. Accordingly, it is preferably vinyl, prop-1- or -2-enyl, but-1-, -2- or -3-enyl, pent-1-, -2-, -3- or -4-enyl, hex-1-, -2-, -3-, -4- or -5-enyl, hept-1-, -2-, -3-, -4-, -5- or -6-enyl. If the two C atoms of the C—C double bond are substituted, the alkenyl radical can be in the form of E and/or Z isomer (trans/cis). In general, the respective E isomers are preferred. Of the alkenyl radicals, prop-2-enyl, but-2- and -3-enyl, and pent-3- and -4-enyl are particularly preferred.

Herein, alkynyl is taken to mean an alkynyl radical having 2 to 15 C atoms, which is straight-chain or branched and contains at least one C—C triple bond. 1- and 2-propynyl and 1-, 2- and 3-butynyl are preferred.

In case R^(F) denotes a halogenated alkyl-, alkoxy-, alkenyl or alkenyloxy it can be branched or unbranched. Preferably it is unbranched, mono-poly or perfluorinated, preferably perfluorinated and has 1, 2, 3, 4, 5, 6 or 7 C atoms, in case of alkenyl 2, 3, 4, 5, 6 or 7 C atoms.

R^(P) preferably denotes CN, NCS, Cl, F, —(CH₂)_(n)—CH═CF₂, —(CH₂)_(n)—CH═CHF, —(CH₂)_(n)—CH═Cl₂, —C_(n)F_(2n+1), —(CF₂)_(n)—CF₂H, —(CH₂)_(n)—CF₃, —(CH₂)_(n)—CHF₂, —(CH₂)_(n)CH₂F, —CH═CF₂, —O(CH₂)_(n)—CH═CF₂, —O(CH₂)_(n)CHCl₂, —OC_(n)F_(2n+1), —O(CF₂)_(n)—CF₂H, —O(CH₂)_(n)CF₃, —O(CH₂)_(n)—CHF₂, —O(CF)_(n)CH₂F, —OCF═CF₂, —SC_(n)F_(2n+1), —S(CF)_(n)—CF₃, wherein n is an integer from 0 to 7.

The compounds of the general formula C are prepared by methods known per se, as described in the literature (for example in the standard works, such as Houben-Weyl, Methoden der organischen Chemie [Methods of Organic Chemistry], Georg-Thieme-Verlag, Stuttgart), to be precise under reaction conditions which are known and are suitable for said reactions. Use can be made here of variants which are known per se, but are not mentioned here in greater detail.

If desired, the starting materials can also be formed in situ by not isolating them from the reaction mixture, but instead by immediately reacting them further into the compounds of the general formula C.

Preferred synthetic pathways towards compounds according to the invention are exemplified in the schemes below, and are further illustrated by means of the working examples. Suitable syntheses are also published for example in Juanli Li, Jian Li, Minggang Hu, Zhaoyi Che, Lingchao Mo, Xiaozhe Yang, Zhongwei An & Lu Zhang (2017) The effect of locations of triple bond at terphenyl skeleton on the properties of isothiocyanate liquid crystals, Liquid Crystals, 44:9, 1374-1383 and can be adapted to the particular desired compounds of the general formula C by choice of suitable starting materials.

Preferred intermediates are 4-bromo-2,6-dichloroaniline and 4-bromo-2-chloro-6-fluoroaniline, both described in the literature, which can be reacted to give compounds of the formula N for example by cross coupling reactions commonly known as Suzuki, Stille, Sonogashira reactions, and the like. Preferred pathways are exemplified in schemes 1 and 2, in which the groups and parameters have the meanings defined in claim 1.

Preferred reagents for the process according to the invention for the transformation of compounds of the formula N into compounds of the formula C (scheme 3) are carbon disulfide, thiophosgene, thiocarbonyl diimidazole, di-2-pyridyl thionocarbonate, bis(dimethylthiocarbamoyl) disulfide, dimethylthiocarbamoyl chloride and phenyl chlorothionoformate, very preferably thiophosgene.

The reactions described should only be regarded as illustrative. The person skilled in the art can carry out corresponding variations of the syntheses described and also follow other suitable synthetic routes in order to obtain compounds of the formula C.

According to a first aspect of the present invention there are provided compounds of formula C in which R^(C) denotes H, alkyl or alkoxy having 1 to 12 C atoms, or alkenyl, alkenyloxy or alkoxyalkyl having 2 to 12 C atoms, in which one or more CH₂-groups may be replaced by

preferably alkyl having 1 to 12 C atoms.

According to a second aspect of the present invention there are provided compounds of formula C in which the group R^(C) denotes R^(P), where R^(P) denotes halogen, CN, NCS, R^(F), R^(F)—O— or R^(F)—S—, and wherein R^(F) denotes fluorinated alkyl or fluorinated alkenyl having up to 9 C atoms, preferably CF₃ or OCF₃.

The compounds of formula C are preferably selected from the compounds in which the groups

-   -    denote

-   -   -   wherein

-   -   -    alternatively denotes

-   -   -    and

    -   L¹ and L² identically or differently, denote F, Cl or straight         chain or branched or cyclic alkyl or alkenyl each having up to         12 C atoms, and

    -   where the other groups and parameters have the meanings given         above.

In a preferred embodiment of the present invention, the compounds of formula C are selected from the compounds of the formulae C-1 to C-11:

-   -   in which     -   L¹, L² and L³ identically or differently, denote H, F, Cl,         methyl, ethyl, n-propyl, isopropyl, cyclopropyl, cyclobutyl,         cyclopentyl or cyclopentenyl, and     -   R^(C) and X have the meanings given above and preferably     -   R^(C) denotes alkyl having 1 to 7 C atoms or a group R^(P),     -   where R^(P) preferably denotes perfluorinated alkoxy having 1 to         7 C atoms, and     -   X denotes F.

Preferably, one of the groups Z^(C1) and Z^(C2) of formula C denotes a single bond and the other one of Z^(C1) and Z^(C2) denotes —C≡C—.

Very preferred compounds of the formula C are selected from the compounds of the following sub-formulae:

-   -   in which R^(C) has the meanings given above and preferably         denotes alkyl having 1 to 7 C atoms or CF₃O.

Very particularly preferred compounds are the compounds of the formulae C-7-1, C-9-1, C-9-4, C-10-1, C-10-2, C-10-3, C-10-4, C-10-5, C-10-6, and C-10-7.

In a preferred embodiment of the present invention the medium comprises one or more compounds selected from the group of compounds of the formulae I, II and III,

-   -   in which     -   R¹ denotes H, unfluorinated alkyl or unfluorinated alkoxy having         1 to 17, preferably 3 to 10 C atoms, or unfluorinated alkenyl,         unfluorinated alkenyloxy or unfluorinated alkoxyalkyl having 2         to 15, preferably 3 to 10, C atoms, in which one or more         CH₂-groups may be replaced by

-   -   -   preferably unfluorinated alkyl or unfluorinated alkenyl,

    -   n is 0, 1 or 2,

-   -   -   on each occurrence, independently of one another, denote

-   -   -   -   in which R^(L), on each occurrence, identically or                 differently, denotes H or alkyl having 1 to 6 C atoms,                 preferably H, methyl or ethyl, particularly preferably                 H,             -   and wherein

-   -   -   -   alternatively denotes

-   -   -   -   preferably

-   -   -   and in case n=2, one of

-   -   -    preferably denotes

-   -   -    and the other preferably denotes

-   -   preferably

-   -   -   independently of one another, denote

-   -   more preferably

-   -    denotes

-   -    denotes

-   -    denotes

-   -   R² denotes H, unfluorinated alkyl or unfluorinated alkoxy having         1 to 17, preferably 3 to 10 C atoms, or unfluorinated alkenyl,         unfluorinated alkenyloxy or unfluorinated alkoxyalkyl having 2         to 15, preferably 3 to 10, C atoms, in which one or more         CH₂-groups may be replaced by

-   -   -   preferably unfluorinated alkyl or unfluorinated alkenyl,

    -   Z²¹ denotes trans-CH═CH—, trans-CF═CF— or —C≡C—, preferably         —C≡C— or trans-CH═CH—, and

-   -   -   independently of one another, denote

-   -   -   -   in which R^(L), on each occurrence, identically or                 differently, denotes H or alkyl having 1 to 6 C atoms,                 preferably H, methyl or ethyl, particularly preferably                 H,             -   and wherein

    -   preferably

-   -   -   independently of one another, denote

-   -   -    preferably denotes

-   -   -    preferably denotes

-   -   -    more preferably

-   -   R³ denotes H, unfluorinated alkyl or unfluorinated alkoxy having         1 to 17, preferably 3 to 10 C atoms, or unfluorinated alkenyl,         unfluorinated alkenyloxy or unfluorinated alkoxyalkyl having 2         to 15, preferably 3 to 10, C atoms, in which one or more         CH₂-groups may be replaced by

-   -   -   preferably unfluorinated alkyl or unfluorinated alkenyl,

    -   one of Z³¹ and Z³², preferably Z³²; denotes trans-CH═CH—,         trans-CF═CF— or —C≡C— and the other one, independently thereof,         denotes —C≡C—, trans-CH═CH—, trans-CF═CF— or a single bond,         preferably one of them, preferably Z³²; denotes —C≡C— or         trans-CH═CH— and the other denotes a single bond, and

-   -   -   independently of one another, denote

-   -   -   -   in which R^(L), on each occurrence, identically or                 differently, denotes H or alkyl having 1 to 6 C atoms,                 preferably H, methyl or ethyl, particularly preferably                 H,             -   and wherein

-   -   -    alternatively denotes

-   -   preferably

-   -   -   independently of one another, denote

-   -   more preferably

-   -    denotes

-   -    denotes

-   -    in particular

-   -    denotes

-   -   -   in particular

In the compounds of the formulae I, II and III, R^(L) preferably denotes H.

In another preferred embodiment, in the compounds of formulae I, II and III, one or two groups R^(L), preferably one group R^(L) is different from H.

In a preferred embodiment of the present invention, the compounds of formula I are selected from the group of compounds of the formulae I-1 to I-5:

-   -   in which     -   L¹, L² and L³ on each occurrence, identically or differently,         denote H or F,     -   and the other groups have the respective meanings indicated         above for formula I and     -   preferably     -   R¹ denotes unfluorinated alkyl having 1 to 7 C atoms or         unfluorinated alkenyl having 2 to 7 C atoms.

The media preferably comprise one or more compounds of formula I-1, which are preferably selected from the group of the compounds of the formulae I-1a to I-1d, preferably of formula I-1b:

-   -   in which R¹ has the meaning indicated above for formula I and         preferably denotes unfluorinated alkyl having 1 to 7 C atoms or         unfluorinated alkenyl having 2 to 7 C atoms.

The media preferably comprise one or more compounds of formula I-2, which are preferably selected from the group of the compounds of the formulae I-2a to I-2e, preferably of formula I-2c:

-   -   in which R¹ has the meaning indicated above for formula I and         preferably denotes unfluorinated alkyl having 1 to 7 C atoms or         unfluorinated alkenyl having 2 to 7 C atoms.

The media preferably comprise one or more compounds of formula I-3, which are preferably selected from the group of the compounds of the formulae I-3a to I-3d, particularly preferably of formula I-3b:

-   -   in which R¹ has the meaning indicated above for formula I and         preferably denotes unfluorinated alkyl having 1 to 7 C atoms or         unfluorinated alkenyl having 2 to 7 C atoms.

The media preferably comprise one or more compounds of formula I-4, which are preferably selected from the group of the compounds of the formulae I-4a to I-4e, particularly preferably of formula I-4b:

-   -   in which R¹ has the meaning indicated above for formula I and         preferably denotes unfluorinated alkyl having 1 to 7 C atoms or         unfluorinated alkenyl having 2 to 7 C atoms.

The media preferably comprise one or more compounds of formula I-5, which are preferably selected from the group of the compounds of the formulae I-5a to I-5d, particularly preferably of formula I-5b:

-   -   in which R¹ has the meaning indicated above for formula I and         preferably denotes unfluorinated alkyl having 1 to 7 C atoms or         unfluorinated alkenyl having 2 to 7 C atoms.

The media preferably comprise one or more compounds of formula II, which are preferably selected from the group of the compounds of the formulae II-1 to II-3, preferably selected from the group of the compounds of the formulae II-1 and II-2:

-   -   in which the occurring groups have the meanings given under         formula above and     -   preferably     -   R² denotes H, unfluorinated alkyl or alkoxy having 1 to 7 C         atoms or unfluorinated alkenyl having 2 to 7 C atoms,     -   and one of

-   -    denotes

-   -   -   and the other, independently denotes

-   -   -   -   preferably

-   -   -   -   most preferably

-   -   and preferably     -   R² denotes C_(n)H_(2n+1) or CH₂═CH—(CH₂)_(Z), and     -   n denotes an integer in the range from 0 to 15, preferably in         the range from 1 to 7 and particularly preferably 1 to 5, and     -   z denotes 0, 1, 2, 3 or 4, preferably 0 or 2.

The compounds of formula II-1 are preferably selected from the group of the compounds of the formulae II-1a to II-1e:

-   -   in which     -   R² has the meaning indicated above and preferably denotes         C_(n)H_(2n+1) or CH₂═CH—(CH₂)_(Z), and     -   n independently of one another, denote an integer in the range         from 0 to 15, preferably in the range from 1 to 7 and         particularly preferably 1 to 5, and     -   z denotes 0, 1, 2, 3 or 4, preferably 0 or 2.

The compounds of formula II-2 are preferably selected from the group of the compounds of the formulae II-2a and II-2b:

-   -   in which     -   R² has the meaning indicated above and preferably denotes         C_(n)H_(2n+1) or CH₂═CH—(CH₂)_(Z),     -   n denotes an integer in the range from 0 to 15, preferably in         the range from 1 to 7 and particularly preferably 1 to 5, and     -   z denotes 0, 1, 2, 3 or 4, preferably 0 or 2.

The compounds of formula II-3 are preferably selected from the group of the compounds of the of formulae II-3a to II-3d:

-   -   in which     -   R² has the meaning indicated above and preferably denotes         C_(n)H_(2n+1) or CH₂═CH—(CH₂)_(Z),     -   n denotes an integer in the range from 0 to 15, preferably in         the range from 1 to 7 and particularly preferably 1 to 5, and     -   z denotes 0, 1, 2, 3 or 4, preferably 0 or 2.

The compounds of formula III are preferably selected from the group of the compounds of the formulae III-1 to III-6, more preferably of the formulae selected from the group of the compounds of the formulae III-1, III-2, III-3 and III-4, and particularly preferably of formula III-1:

-   -   in which     -   Z³¹ and Z³² independently of one another denote trans-CH═CH— or         trans-CF═CF—, preferably trans-CH═CH—, and in formula III-6         alternatively one of Z³¹ and Z³² may denote —C≡C— and the other         groups have the meaning given above under formula III,     -   and preferably     -   R³ denotes H, unfluorinated alkyl or alkoxy having 1 to 7 C         atoms or unfluorinated alkenyl having 2 to 7 C atoms,     -   and one of

-   -    preferably

-   -    denotes

-   -    preferably

-   -   -   and the others, independently of one another, denote

-   -   -   -   preferably

-   -   -   -   more preferably

-   -   where

-   -    alternatively denotes

-   -   and preferably     -   R³ denotes C_(n)H_(2n+1) or CH₂═CH—(CH₂)_(Z),     -   n denotes an integer in the range from 0 to 15, preferably in         the range from 1 to 7 and particularly preferably 1 to 5, and     -   z denotes 0, 1, 2, 3 or 4, preferably 0 or 2.

The compounds of formula III-1 are preferably selected from the group of the compounds of the formulae III-1a to III-1k, more preferably selected from the group of the compounds of the formulae III-1a, III-1b, III-1g and III-1h, particularly preferably of formula III-1b and/or III-1h:

-   -   in which     -   R³ has the meaning indicated above and preferably denotes         C_(n)H_(2n+1) or CH₂═CH—(CH₂)_(Z),     -   n denotes an integer in the range from 0 to 15, preferably in         the range from 1 to 7 and particularly preferably 1 to 5, and     -   z denotes 0, 1, 2, 3 or 4, preferably 0 or 2.

The compounds of formula III-2 are preferably compounds of formula III-2a to III-2l, very preferably III-2b and/or III-2j:

-   -   in which     -   R³ has the meaning indicated above and preferably denotes         C_(n)H_(2n+1) or CH₂═CH—(CH₂)_(Z),     -   n denotes an integer in the range from 0 to 15, preferably in         the range from 1 to 7 and particularly preferably 1 to 5, and     -   z denotes 0, 1, 2, 3 or 4, preferably 0 or 2.

The compounds of formula III-5 are preferably selected from the compounds of formula III-5a:

-   -   R³ has the meaning indicated above for formula III-5 and         preferably denotes C_(n)H_(2n+1), in which     -   n denotes an integer in the range from 0 to 7, preferably in the         range from 1 to 5.

In a preferred embodiment, the media according to the invention comprise one or more compounds selected from the group of compounds of the formulae IIA-1-1 to IIA-1-12, very preferably IIA-1-1 or IIA-1-2:

-   -   in which     -   R¹ denotes alkyl or alkenyl having up to 7 C atoms, preferably         ethyl, n-propyl, n-butyl or n-pentyl, n-hexyl,     -   R^(L) on each occurrence, the same or differently, denotes alkyl         or alkenyl having 1 to 5 C atoms, or cycloalkyl or cycloalkenyl         each having 3 to 6 C atoms, preferably methyl, ethyl, n-propyl,         n-butyl, isopropyl, cyclopropyl, cyclobutyl, cyclopentyl or         cyclopent-1-enyl, very preferably ethyl,     -   and from which the compounds of formula II-1 are excluded.

Additionally, the liquid-crystalline media according to the present invention in a certain embodiment, which may be the same or different from the previous preferred embodiments preferably comprise one or more compounds of formula IV,

-   -   in which

-   -    denotes

-   -   is 0 or 1, preferably 1, and     -   preferably

-   -    denotes

-   -   particularly preferably

-   -   L⁴ denotes H or alkyl having 1 to 6 C atoms, cycloalkyl having 3         to 6 C atoms or cycloalkenyl having 4 to 6 C atoms, preferably         CH₃, C₂H₅, n-C₃H₇, i-C₃H₇, cyclopropyl, cyclobutyl, cyclohexyl,         cyclopent-1-enyl or cyclohex-1-enyl, and particularly preferably         CH₃, C₂H₅, cyclopropyl or cyclobutyl,     -   X⁴ denotes H, alkyl having 1 to 3 C atoms or halogen, preferably         H, F or Cl, more preferably H or F and very particularly         preferably F,     -   R⁴¹ to R⁴⁴, independently of one another, denote unfluorinated         alkyl or unfluorinated alkoxy, each having 1 to 15 C atoms,         unfluorinated alkenyl, unfluorinated alkenyloxy or unfluorinated         alkoxyalkyl, each having 2 to 15 C atoms, or cycloalkyl,         alkylcycloalkyl, cycloalkenyl, alkylcycloalkenyl,         alkylcycloalkylalkyl or alkylcycloalkenylalkyl, each having up         to 15 C atoms, and alternatively one of R⁴³ and R⁴⁴ or both also         denote H,     -   preferably     -   R⁴¹ and R⁴², independently of one another, denote unfluorinated         alkyl or unfluorinated alkoxy, each having 1 to 7 C atoms, or         unfluorinated alkenyl, unfluorinated alkenyloxy or unfluorinated         alkoxyalkyl, each having 2 to 7 C atoms,     -   particularly preferably     -   R⁴¹ denotes unfluorinated alkyl having 1 to 7 C atoms or         unfluorinated alkenyl, unfluorinated alkenyloxy or unfluorinated         alkoxyalkyl, each having 2 to 7 C atoms, and     -   particularly preferably     -   R⁴² denotes unfluorinated alkyl or unfluorinated alkoxy, each         having 1 to 7 C atoms, and     -   preferably     -   R⁴³ and R⁴⁴ denote H, unfluorinated alkyl having 1 to 5 C atoms,         unfluorinated cycloalkyl or cycloalkenyl having 3 to 7 C atoms,         unfluorinated alkylcyclohexyl or unfluorinated cyclohexylalkyl,         each having 4 to 12 C atoms, or unfluorinated         alkylcyclohexylalkyl having 5 to 15 C atoms, particularly         preferably cyclopropyl, cyclobutyl or cyclohexyl, and very         particularly preferably at least one of R⁴³ and R⁴⁴ denotes         n-alkyl, particularly preferably methyl, ethyl or n-propyl, and         the other denotes H or n-alkyl, particularly preferably H,         methyl, ethyl or n-propyl.

In a preferred embodiment of the present invention, the liquid-crystal medium additionally comprises one or more compounds selected from the group of compounds of the formulae V, VI, VII, VIII and IX:

-   -   in which     -   L⁵¹ denotes R⁵¹ or X⁵¹,     -   L⁵² denotes R⁵² or X⁵²,     -   R⁵¹ and R⁵², independently of one another, denote H,         unfluorinated alkyl or unfluorinated alkoxy having 1 to 17,         preferably 3 to 10, C atoms or unfluorinated alkenyl,         unfluorinated alkenyloxy or unfluorinated alkoxyalkyl having 2         to 15, preferably 3 to 10, C atoms, preferably alkyl or         unfluorinated alkenyl,     -   X⁵¹ and X⁵², independently of one another, denote H, F, Cl, —CN,         SF₅, fluorinated alkyl or fluorinated alkoxy having 1 to 7 C         atoms or fluorinated alkenyl, fluorinated alkenyloxy or         fluorinated alkoxyalkyl having 2 to 7 C atoms, preferably         fluorinated alkoxy, fluorinated alkenyloxy, F or Cl, and

-   -   -   independently of one another, denote

-   -   -   preferably

-   -   L⁶¹ denotes R⁶¹ and, in the case where Z⁶¹ and/or Z⁶² denote         trans-CH═CH— or trans-CF═CF—, alternatively also denotes X⁶¹,     -   L⁶² denotes R⁶² and, in the case where Z⁶¹ and/or Z⁶² denote         trans-CH═CH— or trans-CF═CF—, alternatively also denotes X⁶²,     -   R⁶¹ and R⁶², independently of one another, denote H,         unfluorinated alkyl or unfluorinated alkoxy having 1 to 17,         preferably 3 to 10, C atoms or unfluorinated alkenyl,         unfluorinated alkenyloxy or unfluorinated alkoxyalkyl having 2         to 15, preferably 3 to 10, C atoms, preferably alkyl or         unfluorinated alkenyl,     -   X⁶¹ and X⁶², independently of one another, denote F or Cl, —CN,         SF₅, fluorinated alkyl or alkoxy having 1 to 7 C atoms or         fluorinated alkenyl, alkenyloxy or alkoxyalkyl having 2 to 7 C         atoms,     -   one of     -   Z⁶¹ and Z⁶² denotes trans-CH═CH—, trans-CF═CF— or —C≡C— and the         other, independently thereof, denotes trans-CH═CH—, trans-CF═CF—         or a single bond, preferably one of them denotes —C≡C— or         trans-CH═CH— and the other denotes a single bond, and

-   -   -   independently of one another, denote

-   -   -   -   preferably

-   -   and     -   x denotes 0 or 1;     -   L⁷¹ denotes R⁷¹ or X⁷¹,     -   L⁷² denotes R⁷² or X⁷²,     -   R⁷¹ and R⁷², independently of one another, denote H,         unfluorinated alkyl or unfluorinated alkoxy having 1 to 17,         preferably 3 to 10, C atoms or unfluorinated alkenyl,         unfluorinated alkenyloxy or unfluorinated alkoxyalkyl having 2         to 15, preferably 3 to 10, C atoms, preferably alkyl or         unfluorinated alkenyl,     -   X⁷¹ and X⁷², independently of one another, denote H, F, Cl, —CN,         —NCS, —SF₅, fluorinated alkyl or fluorinated alkoxy having 1 to         7 C atoms or fluorinated alkenyl, unfluorinated or fluorinated         alkenyloxy or unfluorinated or fluorinated alkoxyalkyl having 2         to 7 C atoms, preferably fluorinated alkoxy, fluorinated         alkenyloxy, F or Cl, and     -   Z⁷¹ to Z⁷³, independently of one another, denote trans-CH═CH—,         trans-CF═CF—, —C≡C— or a single bond, preferably one or more of         them denote a single bond, particularly preferably all denote a         single bond and

-   -   -   independently of one another, denote

-   -   -   -   preferably

-   -   R⁸¹ and R⁸², independently of one another, denote H,         unfluorinated alkyl or alkoxy having 1 to 15, preferably 3 to         10, C atoms or unfluorinated alkenyl, alkenyloxy or alkoxyalkyl         having 2 to 15, preferably 3 to 10, C atoms, preferably         unfluorinated alkyl or alkenyl,     -   one of     -   Z⁸¹ and Z⁸² denotes trans-CH═CH—, trans-CF═CF— or —C≡C— and the         other, independently thereof, denotes trans-CH═CH—, trans-CF═CF—         or a single bond, preferably one of them denotes —C≡C— or         trans-CH═CH— and the other denotes a single bond, and

-   -    denotes

-   -   -   independently of one another, denote

-   -   L⁹¹ denotes R⁹¹ or X⁹¹,     -   L⁹² denotes R⁹² or X⁹²,     -   R⁹¹ and R⁹², independently of one another, denote H,         unfluorinated alkyl or alkoxy having 1 to 15, preferably 3 to         10, C atoms or unfluorinated alkenyl, alkenyloxy or alkoxyalkyl         having 2 to 15, preferably 3 to 10, C atoms, preferably         unfluorinated alkyl or alkenyl,     -   X⁹¹ and X⁹², independently of one another, denote H, F, Cl, —CN,         —NCS, —SF₅, fluorinated alkyl or fluorinated alkoxy having 1 to         7 C atoms or fluorinated alkenyl, unfluorinated or fluorinated         alkenyloxy or unfluorinated or fluorinated alkoxyalkyl having 2         to 7 C atoms, preferably fluorinated alkoxy, fluorinated         alkenyloxy, F or Cl, and     -   Z⁹¹ to Z⁹³, independently of one another, denote trans-CH═CH—,         trans-CF═CF—, —C≡C— or a single bond, preferably one or more of         them denotes a single bond, and particularly preferably all         denote a single bond,

-   -    denotes

-   -   -   independently of one another, denote

In a preferred embodiment of the present invention, the liquid-crystal medium comprises one or more compounds of the formula V, preferably selected from the group of the compounds of the formulae V-1 to V-3, preferably of the formulae V-1 and/or V-2 and/or V-3, preferably of the formulae V-1 and V-2:

-   -   in which the occurring groups have the respective meanings         indicated above for formula V and preferably     -   R⁵¹ denotes unfluorinated alkyl having 1 to 7 C atoms or         unfluorinated alkenyl having 2 to 7 C atoms,     -   R⁵² denotes unfluorinated alkyl having 1 to 7 C atoms or         unfluorinated alkenyl having 2 to 7 C atoms or unfluorinated         alkoxy having 1 to 7 C atoms,     -   X⁵¹ and X⁵², independently of one another, denote F, Cl, —OCF₃,         —CF₃, —CN or —SF₅, preferably F, Cl, —OCF₃ or —CN.

The compounds of the formula V-1 are preferably selected from the group of the compounds of the formulae V-1a to V-1d, preferably V-1c and V-1d:

-   -   in which the parameters have the respective meanings indicated         above for formula V-1 and in which     -   Y⁵¹ and Y⁵², in each case independently of one another, denote H         or F, and preferably     -   R⁵¹ denotes alkyl or alkenyl, and     -   X⁵¹ denotes F, Cl or —OCF₃.

The compounds of the formula V-2 are preferably selected from the group of the compounds of the formulae V-2a to V-2e and/or from the group of the compounds of the formulae V-2f and V-2g:

-   -   where in each case the compounds of the formula V-2a are         excluded from the compounds of the formulae V-2b and V-2c, the         compounds of the formula V-2b are excluded from the compounds of         the formula V-2c and the compounds of the formula V-2f are         excluded from the compounds of the formula V-2g, and     -   in which the parameters have the respective meanings indicated         above for formula V-1 and in which     -   Y⁵¹ and Y⁵², in each case independently of one another, denote H         or F, and     -   preferably     -   Y⁵¹ and Y⁵² denotes H and the other denotes H or F, preferably         likewise denotes H.

The compounds of the formula V-3 are preferably compounds of the formula V-3a:

-   -   in which the parameters have the respective meanings indicated         above for formula V-1 and in which preferably     -   X⁵¹ denotes F, Cl, preferably F,     -   X⁵² denotes F, Cl or —OCF₃, preferably —OCF₃.

The compounds of the formula V-1a are preferably selected from the group of the compounds of the formulae V-1a-1 and V-1a-2:

-   -   in which     -   R⁵¹ has the meaning indicated above and preferably denotes         C_(n)H_(2n+1), in which     -   n denotes an integer in the range from 1 to 7, preferably in the         range from 1 to 6 and particularly preferably 3 to 5.

The compounds of the formula V-1b are preferably compounds of the formula V-1b-1:

-   -   in which     -   R⁵¹ has the meaning indicated above and preferably denotes         C_(n)H_(2n+1), in which         -   n denotes an integer in the range from 1 to 7, preferably in             the range from 1 to 6 and particularly preferably 3 to 5.

The compounds of the formula V-1c are preferably selected from the group of the compounds of the formulae V-1c-1 to V-1c-4, particularly preferably selected from the group of the compounds of the formulae V-1c-1 and V-1c-2:

-   -   in which     -   R⁵¹ has the meaning indicated above and preferably denotes         C_(n)H_(2n+1), in which     -   n denotes an integer in the range from 1 to 7, preferably in the         range from 1 to 6 and particularly preferably 3 to 5.

The compounds of the formula V-1d are preferably selected from the group of the compounds of the formulae V-1d-1 and V-1d-2, particularly preferably the compound of the formula V-1d-2:

-   -   in which     -   R⁵¹ has the meaning indicated above and preferably denotes         C_(n)H_(2n+1), in which     -   n denotes an integer in the range from 1 to 7, preferably in the         range from 1 to 6 and particularly preferably 3 to 5.

The compounds of the formula V-2a are preferably selected from the group of the compounds of the formulae V-2a-1 and V-2a-2, particularly preferably the compounds of the formula V-2a-1:

-   -   in which     -   R⁵¹ has the meaning indicated above and preferably denotes         C_(n)H_(2n+1) or CH₂═CH—(CH₂)_(Z), and     -   R⁵² has the meaning indicated above and preferably denotes         C_(m)H_(2m+1) or O—C_(m)H_(2m+1) or (CH₂)_(Z)—CH═CH₂, and in         which     -   n and m, independently of one another, denote an integer in the         range from 1 to 7, preferably in the range from 1 to 6 and         particularly preferably 3 to 5, and     -   z denotes 0, 1, 2, 3 or 4, preferably 0 or 2.

Preferred combinations of R⁵¹ with R⁵², in particular in the case of formula V-2a-1, are (C_(n)H_(2n+1) and C_(m)H_(2m+1)), (C_(n)H_(2n+1) and O—C_(m)H_(2m+1)), (CH₂═CH—(CH₂)_(Z) and C_(m)H_(2m+1)), (CH₂═CH—(CH₂)_(Z) and O—C_(m)H_(2m+1)) and (C_(n)H_(2n+1) and (CH₂)_(Z)—CH═CH₂).

Preferred compounds of the formula V-2b are the compounds of the formula V-2b-1:

-   -   in which     -   R⁵¹ has the meaning indicated above and preferably denotes         C_(n)H_(2n+1) or CH₂═CH—(CH₂)_(Z), and     -   R⁵² has the meaning indicated above and preferably denotes         C_(m)H_(2m+1) or O—C_(m)H_(2m+1) or (CH₂)_(Z)—CH═CH₂, and in         which     -   n and m, independently of one another, denote an integer in the         range from 1 to 7, preferably in the range from 1 to 6 and         particularly preferably 3 to 5, and     -   z denotes 0, 1, 2, 3 or 4, preferably 0 or 2.

The preferred combination of R⁵¹ with R⁵² here is, in particular, C_(n)H_(2n+1) and C_(m)H_(2m+1). Preferred compounds of the formula V-2c are the compounds of the formula V-2c-1:

-   -   in which     -   R⁵¹ has the meaning indicated above and preferably denotes         C_(n)H_(2n+1) or CH₂═CH—(CH₂)_(Z), and     -   R⁵² has the meaning indicated above and preferably denotes         C_(m)H_(2m+1) or O—C_(m)H_(2m+1) or (CH₂)_(Z)—CH═CH₂, and in         which     -   n and m, independently of one another, denote an integer in the         range from 1 to 7, preferably in the range from 1 to 6 and         particularly preferably 3 to 5, and     -   z denotes 0, 1, 2, 3 or 4, preferably 0 or 2.

The preferred combination of (R⁵¹ and R⁵²) here is, in particular, (C_(n)H_(2n+1) and C_(m)H_(2m+1)).

Preferred compounds of the formula V-2d are the compounds of the formula V-2d-1:

-   -   in which     -   R⁵¹ has the meaning indicated above and preferably denotes         C_(n)H_(2n+1) or CH₂═CH—(CH₂)_(Z), and     -   R⁵² has the meaning indicated above and preferably denotes         C_(m)H_(2m+1) or O—C_(m)H_(2m+1) or (CH₂)_(Z)—CH═CH₂, and in         which     -   n and m, independently of one another, denote an integer in the         range from 1 to 7, preferably in the range from 1 to 6 and         particularly preferably 3 to 5, and     -   z denotes 0, 1, 2, 3 or 4, preferably 0 or 2.

The preferred combination of (R⁵¹ and R⁵²) here is, in particular, (C_(n)H_(2n+1) and C_(m)H_(2m+1)). Preferred compounds of the formula V-2e are the compounds of the formula V-2e-1:

-   -   in which     -   R⁵¹ has the meaning indicated above and preferably denotes         C_(n)H_(2n+1) or CH₂═CH—(CH₂)_(Z), and     -   R⁵² has the meaning indicated above and preferably denotes         C_(m)H_(2m+1) or O—C_(m)H_(2m+1) or (CH₂)_(Z)—CH═CH₂, and in         which     -   n and m, independently of one another, denote an integer in the         range from 1 to 7, preferably in the range from 2 to 6 and         particularly preferably 3 to 5, and     -   z denotes 0, 1, 2, 3 or 4, preferably 0 or 2.

The preferred combination of (R⁵¹ and R⁵²) here is, in particular, (C_(n)H_(2n+1) and O—C_(m)H_(2m+1)).

Preferred compounds of the formula V-2f are the compounds of the formula V-2f-1:

-   -   in which     -   R⁵¹ has the meaning indicated above and preferably denotes         C_(n)H_(2n+1) or CH₂═CH—(CH₂)_(Z), and     -   R⁵² has the meaning indicated above and preferably denotes         C_(m)H_(2m+1) or O—C_(m)H_(2m+1) or (CH₂)_(Z)—CH═CH₂, and in         which     -   n and m, independently of one another, denote an integer in the         range from 1 to 7, preferably in the range from 2 to 6 and         particularly preferably 3 to 5, and     -   z denotes 0, 1, 2, 3 or 4, preferably 0 or 2.

The preferred combinations of (R⁵¹ and R⁵²) here are, in particular, (C_(n)H_(2n+1) and C_(m)H_(2m+1)) and (C_(n)H_(2n+1) and O—C_(m)H_(2m+1)), particularly preferably (C_(n)H_(2n+1) and C_(m)H_(2m+1)).

Preferred compounds of the formula V-2g are the compounds of the formula V-2g-1:

-   -   in which     -   R⁵¹ has the meaning indicated above and preferably denotes         C_(n)H_(2n+1) or CH₂═CH—(CH₂)_(Z), and     -   R⁵² has the meaning indicated above and preferably denotes         C_(m)H_(2m+1) or O—C_(m)H_(2m+1) or (CH₂)_(Z)—CH═CH₂, and in         which     -   n and m, independently of one another, denote an integer in the         range from 1 to 7, preferably in the range from 2 to 6 and         particularly preferably 3 to 5, and     -   z denotes 0, 1, 2, 3 or 4, preferably 0 or 2.

The preferred combinations of (R⁵¹ and R⁵²) here are, in particular, (C_(n)H_(2n+1) and C_(m)H_(2m+1)) and (C_(n)H_(2n+1) and O—C_(m)H_(2m+1)), particularly preferably (C_(n)H_(2n+1) and O—C_(m)H_(2m+1)).

The compounds of the formula VI are preferably selected from the group of the compounds of the formulae VI-1 to VI-5:

-   -   in which     -   Z⁶¹ and Z⁶² denote —C≡C—, trans-CH═CH— or trans-CF═CF—,         preferably —C≡C— or trans-CH═CH—, and the other occurring groups         and parameters have the meaning given above under formula VI,     -   and preferably     -   R⁶¹ and R⁶², independently of one another, denote H,         unfluorinated alkyl or alkoxy having 1 to 7 C atoms or         unfluorinated alkenyl having 2 to 7 C atoms,     -   X⁶² denotes F, Cl, —OCF₃ or —CN,

The compounds of the formula VI-1 are preferably selected from the group of the compounds of the formulae VI-1a and VI-1b, more preferably selected from compounds of the formula VI-1a:

-   -   in which     -   R⁶¹ has the meaning indicated above and preferably denotes         C_(n)H_(2n+1) or CH₂═CH—(CH₂)_(Z), and     -   R⁶² has the meaning indicated above and preferably denotes         C_(m)H_(2m+1) or O—C_(m)H_(2m+1) or (CH₂)_(Z)—CH═CH₂, and in         which     -   n and m, independently of one another, denote an integer in the         range from 1 to 7, preferably in the range from 2 to 6 and         particularly preferably 3 to 5, and     -   z denotes 0, 1, 2, 3 or 4, preferably 0 or 2.

The preferred combinations of (R⁶¹ and R⁶²) here are, in particular, (C_(n)H_(2n+1) and C_(m)H_(2m+1)) and (C_(n)H_(2n+1) and O—C_(m)H_(2m+1)), in the case of formula VI-1a particularly preferably (C_(n)H_(2n+1) and C_(m)H_(2m+1)) and in the case of formula VI-1b particularly preferably (C_(n)H_(2n+1) and O—C_(m)H_(2m+1)).

The compounds of the formula VI-3 are preferably selected from the compounds of the formula VI-3a to VI-3e:

-   -   in which the parameters have the meaning given above under         formula VI-3 and preferably     -   R⁶¹ has the meaning indicated above and preferably denotes         C_(n)H_(2n+1), in which     -   n denotes an integer in the range from 1 to 7, preferably in the         range from 1 to 5, and     -   X⁶² denotes —F, —Cl, —OCF₃, or —CN.

The compounds of the formula VI-4 are preferably selected from compounds of the formulae VI-4a to VI-4e:

-   -   in which the parameters have the meaning given above under         formula VI-4 and preferably     -   R⁶¹ has the meaning indicated above and preferably denotes         C_(n)H_(2n+1), in which     -   n denotes an integer in the range from 1 to 7, preferably in the         range from 1 to 5, and     -   X⁶² denotes F, Cl, OCF₃, or —CN.

The compounds of the formula VI-5 are preferably selected from the compounds of the formulae VI-5a to VI-5d, preferably VI-5b:

-   -   in which the parameters have the meaning given above under         formula VI-5 and preferably     -   R⁶¹ has the meaning indicated above and preferably denotes         C_(n)H_(2n+1), in which     -   n denotes an integer in the range from 1 to 7, preferably in the         range from 1 to 5, and     -   X⁶² denotes —F, —Cl, —OCF₃, or —CN, particularly preferably         —OCF₃.

The compounds of the formula VII are preferably selected from the group of the compounds of the formulae VII-1 to VII-6:

-   -   where the compounds of the formula VII-5 are excluded from the         compounds of the formula VII-6, and     -   in which the parameters have the respective meanings indicated         above for formula VII,     -   Y⁷¹, Y⁷², Y⁷³ independently from one another, denote H or F,     -   and preferably     -   R⁷¹ denotes unfluorinated alkyl or alkoxy, each having 1 to 7 C         atoms, or unfluorinated alkenyl having 2 to 7 C atoms,     -   R⁷² denotes unfluorinated alkyl or alkoxy, each having 1 to 7 C         atoms, or unfluorinated alkenyl having 2 to 7 C atoms,     -   X⁷² denotes F, Cl; NCS or —OCF₃, preferably F or NCS, and     -   particularly preferably     -   R⁷¹ has the meaning indicated above and preferably denotes         C_(n)H_(2n+1) or CH₂═CH—(CH₂)_(Z), and     -   R⁷² has the meaning indicated above and preferably denotes         C_(m)H_(2m+1) or O—C_(m)H_(2m+1) or (CH₂)_(Z)—CH═CH₂, and in         which     -   n and m, independently of one another, denote an integer in the         range from 1 to 7, preferably in the range from 2 to 6 and         particularly preferably 3 to 5, and     -   z denotes 0, 1, 2, 3 or 4, preferably 0 or 2.

The compounds of the formula VII-1 are preferably selected from the group of the compounds of the formulae VII-1a to VII-1d:

-   -   in which X⁷² has the meaning given above for formula VII-2 and     -   R⁷¹ has the meaning indicated above and preferably denotes         C_(n)H_(2n+1), in which     -   n denotes an integer in the range from 1 to 7, preferably in the         range from 2 to 6 and particularly preferably 3 to 5, and     -   z denotes 0, 1, 2, 3 or 4, preferably 0 or 2, and     -   X⁷² preferably denotes F.

The compounds of the formula VII-2 are preferably selected from the group of the compounds of the formulae VII-2a and VII-2b, particularly preferably of the formula VII-2a:

-   -   in which     -   R⁷¹ has the meaning indicated above and preferably denotes         C_(n)H_(2n+1) or CH₂═CH—(CH₂)_(Z), and     -   R⁷² has the meaning indicated above and preferably denotes         C_(m)H_(2m+1) or O—C_(m)H_(2m+1) or (CH₂)_(Z)—CH═CH₂, and in         which     -   n and m, independently of one another, denote an integer in the         range from 1 to 7, preferably in the range from 2 to 6 and         particularly preferably 3 to 5, and     -   z denotes 0, 1, 2, 3 or 4, preferably 0 or 2.

The preferred combinations of (R⁷¹ and R⁷²) here are, in particular, (C_(n)H_(2n+1) and C_(m)H_(2m+1)) and (C_(n)H_(2n+1) and O—C_(m)H_(2m+1)), particularly preferably (C_(n)H_(2n+1) and C_(m)H_(2m+1)).

The compounds of the formula VII-3 are preferably compounds of the formula VII-3a:

-   -   in which     -   R⁷¹ has the meaning indicated above and preferably denotes         C_(n)H_(2n+1) or CH₂═CH—(CH₂)_(Z), and     -   R⁷² has the meaning indicated above and preferably denotes         C_(m)H_(2m+1) or O—C_(m)H_(2m+1) or (CH₂)_(Z)—CH═CH₂, and in         which     -   n and m, independently of one another, denote an integer in the         range from 1 to 7, preferably in the range from 2 to 6 and         particularly preferably 3 to 5, and     -   z denotes 0, 1, 2, 3 or 4, preferably 0 or 2.

The preferred combinations of (R⁷¹ and R⁷²) here are, in particular, (C_(n)H_(2n+1) and C_(m)H_(2m+1)) and (C_(n)H_(2n+1) and O—C_(m)H_(2m+1)), particularly preferably (C_(n)H_(2n+1) and C_(m)H_(2m+1)).

The compounds of the formula VII-4 are preferably compounds of the formula VII-4a:

-   -   in which     -   R⁷¹ has the meaning indicated above and preferably denotes         C_(n)H_(2n+1) or CH₂═CH—(CH₂)_(Z), and     -   R⁷² has the meaning indicated above and preferably denotes         C_(m)H_(2m+1) or O—C_(m)H_(2m+1) or (CH₂)_(Z)—CH═CH₂, and in         which     -   n and m, independently of one another, denote an integer in the         range from 1 to 7, preferably in the range from 2 to 6 and         particularly preferably 3 to 5, and     -   z denotes 0, 1, 2, 3 or 4, preferably 0 or 2.

The preferred combinations of (R⁷¹ and R⁷²) here are, in particular, (C_(n)H_(2n+1) and C_(m)H_(2m+1)) and (C_(n)H_(2n+1) and O—C_(m)H_(2m+1)), particularly preferably (C_(n)H_(2n+1) and C_(m)H_(2m+1)).

The compounds of the formula VII-5 are preferably selected from the group of the compounds of the formulae VII-5a and VII-5b, more preferably of the formula VII-5a:

-   -   in which     -   R⁷¹ has the meaning indicated above and preferably denotes         C_(n)H_(2n+1) or CH₂═CH—(CH₂)_(Z), and     -   R⁷² has the meaning indicated above and preferably denotes         C_(m)H_(2m+1) or O—C_(m)H_(2m+1) or (CH₂)_(Z)—CH═CH₂, and in         which     -   n and m, independently of one another, denote an integer in the         range from 1 to 7, preferably in the range from 2 to 6 and         particularly preferably 3 to 5, and     -   z denotes 0, 1, 2, 3 or 4, preferably 0 or 2.

The preferred combinations of (R⁷¹ and R⁷²) here are, in particular, (C_(n)H_(2n+1) and C_(m)H_(2m+1)) and (C_(n)H_(2n+1) and O—C_(m)H_(2m+1)), particularly preferably (C_(n)H_(2n+1) and C_(m)H_(2m+1)).

The compounds of the formula VII-6 are preferably selected from the group of the compounds of the formulae VII-6a and VII-6b:

-   -   in which     -   R⁷¹ has the meaning indicated above and preferably denotes         C_(n)H_(2n+1) or CH₂═CH—(CH₂)_(Z), and     -   R⁷² has the meaning indicated above and preferably denotes         C_(m)H_(2m+1) or O—C_(m)H_(2m+1) or (CH₂)_(Z)—CH═CH₂, and in         which     -   n and m, independently of one another, denote an integer in the         range from 1 to 7, preferably in the range from 2 to 6 and         particularly preferably 3 to 5, and     -   z denotes 0, 1, 2, 3 or 4, preferably 0 or 2.

The preferred combinations of (R⁷¹ and R⁷²) here are, in particular, (C_(n)H_(2n+1) and C_(m)H_(2m+1)) and (C_(n)H_(2n+1) and O—C_(m)H_(2m+1)), particularly preferably (C_(n)H_(2n+1) and C_(m)H_(2m+1)).

The compounds of the formula VII-7 are preferably selected from the group of the compounds of the formulae VII-7a to VII-7d:

-   -   in which     -   R⁷¹ has the meaning indicated above and preferably denotes         C_(n)H_(2n+1) or CH₂═CH—(CH₂)_(Z),     -   X⁷² denotes F, —OCF₃ or —NCS,     -   n denotes an integer in the range from 1 to 7, preferably in the         range from 2 to 6 and particularly preferably 3 to 5, and     -   z denotes 0, 1, 2, 3 or 4, preferably 0 or 2.

The compounds of the formula VIII are preferably selected from the group of the compounds of the formulae VIII-1 to VIII-3, more preferably these compounds of the formula VIII predominantly consist, even more preferably essentially consist and very particularly preferably completely consist thereof:

-   -   in which     -   one of     -   Y⁸¹ and Y⁸² denotes H and the other denotes H or F, and     -   R⁸¹ has the meaning indicated above and preferably denotes         C_(n)H_(2n+1) or CH₂═CH—(CH₂)_(Z), and     -   R⁸² has the meaning indicated above and preferably denotes         C_(m)H_(2m+1) or O—C_(m)H_(2m+1) or (CH₂)_(Z)—CH═CH₂, and in         which     -   n and m, independently of one another, denote an integer in the         range from 1 to 7, preferably in the range from 2 to 6 and         particularly preferably 3 to 5, and     -   z denotes 0, 1, 2, 3 or 4, preferably 0 or 2.

The preferred combinations of (R⁸¹ and R⁸²) here are, in particular, (C_(n)H_(2n+1) and C_(m)H_(2m+1)) and (C_(n)H_(2n+1) and O—C_(m)H_(2m+1)), particularly preferably (C_(n)H_(2n+1) and C_(m)H_(2m+1)).

The compounds of the formula VIII-1 are preferably selected from the group of the compounds of the formulae VIII-1a to VIII-1c:

-   -   in which     -   R⁸¹ has the meaning indicated above and preferably denotes         C_(n)H_(2n+1) or CH₂═CH—(CH₂)_(Z), and     -   R⁸² has the meaning indicated above and preferably denotes         C_(m)H_(2m+1) or O—C_(m)H_(2m+1) or (CH₂)_(Z)—CH═CH₂, and in         which     -   n and m, independently of one another, denote an integer in the         range from 1 to 7, preferably in the range from 2 to 6 and         particularly preferably 3 to 5, and     -   z denotes 0, 1, 2, 3 or 4, preferably 0 or 2.

The preferred combinations of (R⁸¹ and R⁸²) here are, in particular, (C_(n)H_(2n+1) and C_(m)H_(2m+1)) and (C_(n)H_(2n+1) and O—C_(m)H_(2m+1)), particularly preferably (C_(n)H_(2n+1) and C_(m)H_(2m+1)).

The compounds of the formula VIII-2 are preferably compounds of the formula VIII-2a:

-   -   in which     -   R⁸¹ has the meaning indicated above and preferably denotes         C_(n)H_(2n+1) or CH₂═CH—(CH₂)_(Z), and     -   R⁸² has the meaning indicated above and preferably denotes         C_(m)H_(2m+1) or O—C_(m)H_(2m+1) or (CH₂)_(Z)—CH═CH₂, and in         which     -   n and m, independently of one another, denote an integer in the         range from 1 to 7, preferably in the range from 2 to 6 and         particularly preferably 3 to 5, and     -   z denotes 0, 1, 2, 3 or 4, preferably 0 or 2.

The preferred combinations of (R⁸¹ and R⁸²) here are, in particular, (C_(n)H_(2n+1) and C_(m)H_(2m+1)), (C_(n)H_(2n+1) and O—C_(m)H_(2m+1)) and (CH₂═CH—(CH₂)_(Z) and C_(m)H_(2m+1)), particularly preferably (C_(n)H_(2n+1) and C_(m)H_(2m+1)).

The compounds of the formula VIII-3 are preferably compounds of the formula VIII-3a:

-   -   in which     -   R⁸¹ has the meaning indicated above and preferably denotes         C_(n)H_(2n+1) or CH₂═CH—(CH₂)_(Z), and     -   R⁸² has the meaning indicated above and preferably denotes         C_(m)H_(2m+1) or O—C_(m)H_(2m+1) or (CH₂)_(Z)—CH═CH₂, and in         which     -   n and m, independently of one another, denote an integer in the         range from 1 to 7, preferably in the range from 2 to 6 and         particularly preferably 3 to 5, and     -   z denotes 0, 1, 2, 3 or 4, preferably 0 or 2.

The preferred combinations of (R⁸¹ and R⁸²) here are, in particular, (C_(n)H_(2n+1) and C_(m)H_(2m+1)) and (C_(n)H_(2n+1) and O—C_(m)H_(2m+1)).

The compounds of the formula IX are preferably selected from the group of the compounds of the formulae IX-1 to IX-3:

-   -   in which the parameters have the respective meaning indicated         above under formula IX and preferably     -   one of

-   -   -   denotes

-   -   and in which     -   R⁹¹ has the meaning indicated above and preferably denotes         C_(n)H_(2n+1) or CH₂═CH—(CH₂)_(Z), and     -   R⁹² has the meaning indicated above and preferably denotes         C_(m)H_(2m+1) or O—C_(m)H_(2m+1) or (CH₂)_(Z)—CH═CH₂, and in         which     -   n and m, independently of one another, denote an integer in the         range from 1 to 7, preferably in the range from 2 to 6 and         particularly preferably 3 to 5, and     -   z denotes 0, 1, 2, 3 or 4, preferably 0 or 2.

The preferred combinations of (R⁹¹ and R⁹²) here are, in particular, (C_(n)H_(2n+1) and C_(m)H_(2m+1)) and (C_(n)H_(2n+1) and O—C_(m)H_(2m+1)).

The compounds of the formula IX-1 are preferably selected from the group of the compounds of the formulae IX-1a to IX-1e:

-   -   in which the parameters have the meaning given above and         preferably     -   R⁹¹ has the meaning indicated above and preferably denotes         C_(n)H_(2n+1), and     -   n denotes an integer in the range from 0 to 15, preferably in         the range from 1 to 7 and particularly preferably 1 to 5, and     -   X⁹² preferably denotes F or Cl.

The compounds of the formula IX-2 are preferably selected from the group of the compounds of the formulae IX-2a and IX-2b:

-   -   in which     -   R⁹¹ has the meaning indicated above and preferably denotes         C_(n)H_(2n+1) or CH₂═CH—(CH₂)_(Z), and     -   R⁹² has the meaning indicated above and preferably denotes         C_(m)H_(2m+1) or O—C_(m)H_(2m+1) or (CH₂)_(Z)—CH═CH₂, and in         which     -   n and m, independently of one another, denote an integer in the         range from 1 to 7, preferably in the range from 2 to 6 and         particularly preferably 3 to 5, and     -   z denotes 0, 1, 2, 3 or 4, preferably 0 or 2.

The preferred combination of (R⁹¹ and R⁹²) here is, in particular, (C_(n)H_(2n+1) and C_(m)H_(2m+1)).

The compounds of the formula IX-3 are preferably compounds of the formulae IX-3a and IX-3b:

-   -   in which     -   R⁹¹ has the meaning indicated above and preferably denotes         C_(n)H_(2n+1) or CH₂═CH—(CH₂)_(Z), and     -   R⁹² has the meaning indicated above and preferably denotes         C_(m)H_(2m+1) or O—C_(m)H_(2m+1) or (CH₂)_(Z)—CH═CH₂, and in         which     -   n and m, independently of one another, denote an integer in the         range from 1 to 7, preferably in the range from 2 to 6 and         particularly preferably 3 to 5, and     -   z denotes 0, 1, 2, 3 or 4, preferably 0 or 2.

The preferred combinations of (R⁹¹ and R⁹²) here are, in particular, (C_(n)H_(2n+1) and C_(m)H_(2m+1)) and (C_(n)H_(2n+1) and O—C_(m)H_(2m+1)), particularly preferably (C_(n)H_(2n+1) and O—C_(m)H_(2m+1)).

In a preferred embodiment of the present invention the medium comprises one or more compounds of formula X

-   -   in which     -   R¹⁰¹ denotes H, alkyl or alkoxy having 1 to 15, preferably 3 to         10, C atoms or unfluorinated alkenyl, unfluorinated alkenyloxy         or unfluorinated alkoxyalkyl having 2 to 15, preferably 3 to 10,         C atoms, preferably alkyl or alkenyl,     -   X¹⁰¹ denotes H, F, Cl, —CN, SF₅, NCS, fluorinated alkyl or         fluorinated alkoxy having 1 to 7 C atoms or fluorinated alkenyl,         fluorinated alkenyloxy or fluorinated alkoxyalkyl having 2 to 7         C atoms, preferably fluorinated alkoxy, fluorinated alkenyloxy,         F, Cl or NCS, particularly preferably NCS,     -   Y¹⁰¹ denotes methyl, ethyl or Cl,     -   Y¹⁰² denotes H, methyl, ethyl, F or Cl, preferably H or F,     -   Z¹⁰¹, Z¹⁰² identically or differently, denote a single bond,         —CH═CH—, —CF═CF— or —C≡C—,

-   -    independently of one another, denote

-   -   -   preferably

-   -   and where

-   -    alternatively denotes

-   -    and     -   n is 0 or 1.

Preferably, the compounds of formula X are selected from the sub-formulae X-1 and X-2

-   -   in which the occurring groups and parameters have the meanings         given above for formula X.

Particularly preferably, the media according to the invention comprise one or more compounds selected from the group of compounds of the formulae X-1-1 to X-1-9

In a preferred embodiment, the medium according to the invention comprises one or more compounds of formula XI

-   -   in which     -   R^(S) denotes H, alkyl or alkoxy having 1 to 12 C atoms, or         alkenyl, alkenyloxy or alkoxyalkyl having 2 to 12 C atoms, in         which one or more CH₂-groups may be replaced by

-   -    and in which one or more H atoms may be replaced by F,

-   -   -   on each occurrence, independently of one another, denote

-   -   -   in which R^(L), on each occurrence identically or             differently, denotes H, Cl or straight chain, branched or             cyclic alkyl having 1 to 6 C atoms,

    -   L^(S1), L^(S2) identically or differently, denote H, Cl or F,

    -   R^(S1), R^(S2), identically or differently, denote H, alkyl or         alkenyl, having up to 6 C atoms, or cyclopropyl, cyclobutyl,         cyclopentenyl, or cyclopentyl,

    -   R^(Th1), R^(Th2) identically or differently, denote H, alkyl or         alkenyl or alkoxy, having up to 6 C atoms, or cyclopropyl,         cyclobutyl, cyclopentenyl or cyclopentyl,

    -   Z^(S1), Z^(S2), Z^(S3) identically or differently, denote         —CH═CH—, —CH═CF—, —CF═CH—, —CF═CF—, —C≡C—, or a single bond,

    -   a, b identically or differently, are 0 or 1.

Preferably, the compounds of formula XI are selected from the group of compounds of the formulae XI-1 to XI-24:

-   -   in which the occurring groups have the meanings given above for         formula XI and preferably     -   R^(S) denotes alkyl or alkenyl having 2 to 6 C atoms, in which         one or more CH₂-groups may be replaced by

-   -   R^(S1) and R^(S2) identically or differently, denote H or alkyl         having 1 to 6 C atoms, preferably H,     -   R^(S3) denotes H, F or alkyl, having up to 6 C atoms, or         cyclopropyl, preferably H, F or ethyl, very preferably H,     -   L^(S1) and L^(S2) identically or differently, denote H or F,         preferably F.

Preferably, the medium according to the invention comprises one or more compounds of formula T

-   -   in which     -   R^(T) denotes halogen, CN, NCS, R^(F), R^(F)—O— or R^(F)—S—,         wherein     -   R^(F) denotes fluorinated alkyl or fluorinated alkenyl having up         to 12 C atoms,

-   -   -   on each occurrence, independently of one another, denote

-   -   L⁴ and L⁵ identically or differently, denote F, Cl or straight         chain or branched or cyclic alkyl or alkenyl each having up to         12 C atoms;     -   Z^(T3), Z^(T4) identically or differently, denote —CH═CH—,         —CF═CF—,     -    —CH═CF—, —CF═CH—, —C≡C— or a single bond, and     -   t is 0 or 1.

In a preferred embodiment, the liquid crystalline media according to the invention comprise one or more compounds selected from the group of compounds of the formulae T-1a to T-3b below:

-   -   in which

-   -    have the meanings given above and     -   n is 1, 2, 3, 4, 5, 6 or 7, preferably 1, 2, 3 or 4,         particularly preferably 1.

In a particularly preferred embodiment of the present invention the media comprise one or more compounds selected from the compounds of the formulae T-1a and T-2a.

Preferred compounds of formula T-1a are selected from the group of compounds of the following sub-formulae:

-   -   in which n is 1, 2, 3 or 4, preferably 1.

Preferred compounds of formula T-2a are selected from the group of compounds of the following sub-formulae:

-   -   in which n is 1, 2, 3 or 4, preferably 1.

Very preferably, the medium according to the invention comprises one or more compounds of formula T-1a-5.

The media according to the present invention comprise one or more chiral dopants. Preferably these chiral dopants have an absolute value of the helical twisting power (HTP) in the range of from 1 μm⁻¹ to 150 μm⁻¹, preferably in the range of from 10 μm⁻¹ to 100 μm⁻¹. In case the media comprise two or more chiral dopants, these may have opposite signs of their HTP-values. This condition is preferred for some specific embodiments, as it allows to compensate the chirality of the respective compounds to some degree and, thus, may be used to compensate various temperature dependent properties of the resulting media in the devices. Generally, however, it is preferred that most, preferably all of the chiral compounds present in the media according to the present invention have the same sign of their HTP-values.

Preferably the chiral dopants present in the media according to the instant application are mesogenic compounds and most preferably they exhibit a mesophase on their own.

In a preferred embodiment of the present invention, the medium comprises two or more chiral compounds which all have the same algebraic sign of the HTP.

The temperature dependence of the HTP of the individual compounds may be high or low. The temperature dependence of the pitch of the medium can be compensated by mixing compounds having different temperature dependencies of the HTP in corresponding ratios.

For the optically active component, a multitude of chiral dopants, some of which are commercially available, is available to the person skilled in the art, such as, for example, cholesteryl nonanoate, R- and S-811, R- and S-1011, R- and S-2011, R- and S-3011, R- and S-4011, or CB15 (all Merck KGaA, Darmstadt).

Particularly suitable dopants are compounds which contain one or more chiral groups and one or more mesogenic groups, or one or more aromatic or alicyclic groups which form a mesogenic group with the chiral group.

Suitable chiral groups are, for example, chiral branched hydrocarbon radicals, chiral ethane diols, binaphthols or dioxolanes, furthermore mono- or polyvalent chiral groups selected from the group consisting of sugar derivatives, sugar alcohols, sugar acids, lactic acids, chiral substituted glycols, steroid derivatives, terpene derivatives, amino acids or sequences of a few, preferably 1-5, amino acids.

Preferred chiral groups are sugar derivatives, such as glucose, mannose, galactose, fructose, arabinose and dextrose; sugar alcohols, such as, for example, sorbitol, mannitol, iditol, galactitol or anhydro derivatives thereof, in particular dianhydrohexitols, such as dianhydrosorbide (1,4:3,6-dianhydro-D-sorbide, isosorbide), dianhydromannitol (isosorbitol) or dianhydroiditol (isoiditol); sugar acids, such as, for example, gluconic acid, gluconic acid and ketogulonic acid; chiral substituted glycol radicals, such as, for example, mono- or oligoethylene or propylene glycols, in which one or more CH₂ groups are substituted by alkyl or alkoxy; amino acids, such as, for example, alanine, valine, phenylglycine or phenylalanine, or sequences of from 1 to 5 of these amino acids; steroid derivatives, such as, for example, cholesteryl or cholic acid radicals; terpene derivatives, such as, for example, menthyl, neomenthyl, campheyl, pineyl, terpineyl, isolongifolyl, fenchyl, carreyl, myrthenyl, nopyl, geraniyl, linaloyl, neryl, citronellyl or dihydrocitronellyl.

The media according to the present invention preferably comprise chiral dopants which are selected from the group of known chiral dopants. Suitable chiral groups and mesogenic chiral compounds are described, for example, in DE 34 25 503, DE 35 34 777, DE 35 34 778, DE 35 34 779 and DE 35 34 780, DE 43 42 280, EP 01 038 941 and DE 195 41 820. Examples are also compounds listed in Table F below.

Chiral compounds preferably used according to the present invention are selected from the group consisting of the formulae shown below.

Particular preference is given to chiral dopants selected from the group consisting of compounds of the following formulae A-I to A-III and A-Ch:

-   -   in which     -   R^(a11), R^(a12) and R^(b12), independently of one another,         denote alkyl having 1 to 15 C atoms, in which, in addition, one         or more non-adjacent CH₂ groups may each be replaced,         independently of one another, by —C(R^(z))═C(R^(z))—, —C≡C—,         —O—, —S—, —CO—, —CO—O—, —O—CO— or —O—CO—O— in such a way that O         and/or S atoms are not linked directly to one another, and in         which, in addition, one or more H atoms may each be replaced by         F, Cl, Br, I or CN, preferably alkyl, more preferably n-alkyl,         with the proviso that R^(a12) is different from R^(b12),     -   R^(a21) and R^(a22), independently of one another, denote alkyl         having 1 to 15 C atoms, in which, in addition, one or more         non-adjacent CH₂ groups may each be replaced, independently of         one another, by —C(R^(z))═C(R^(z))—, —C≡C—, —O—, —S—, —CO—,         —CO—O—, —O—CO— or —O—CO—O— in such a way that O and/or S atoms         are not linked directly to one another, and in which, in         addition, one or more H atoms may be replaced by F, Cl, Br, I or         CN, preferably both are alkyl, more preferably n-alkyl,     -   R^(a31), R^(a32) and R^(b32), independently of one another,         denote straight-chain or branched alkyl having 1 to 15 C atoms,         in which, in addition, one or more non-adjacent CH₂ groups may         each be replaced, independently of one another, by         —C(R^(z))═C(R^(z))—,         -   —C≡C—, —O—, —S—, —CO—, —CO—O—, —O—CO— or —O—CO—O— in such a             way that O and/or S atoms are not linked directly to one             another, and in which, in addition, one or more H atoms may             be replaced by F, Cl, Br, I or CN, preferably alkyl, more             preferably n-alkyl, with the proviso that R^(a32) is             different from R^(b32);     -   R^(z) denotes H, CH₃, F, Cl, or CN, preferably H or F,     -   R⁸ has one of the meanings of R^(a11) given above, preferably         alkyl, more preferably n-alkyl having 1 to 15 C atoms,     -   Z⁸ denotes —C(O)O—, CH₂O, CF₂O or a single bond, preferably         —C(O)O—,     -   A¹¹ is defined as A¹² below, or alternatively denotes

-   -   A¹² denotes

-   -   -   preferably

-   -   -   in which         -   L¹² on each occurrence, independently of one another,             denotes halogen, CN, or alkyl, alkenyl, alkoxy or alkenyloxy             having up to 12 C atoms and in which one or more H atoms are             optionally replaced with halogen, preferably methyl, ethyl,             Cl or F, particularly preferably F,

    -   A²¹ denotes

-   -   A²² has the meanings given for A¹²     -   A³¹ has the meanings given for A¹¹,         -   or alternatively denotes

-   -   A³² has the meanings given for A¹².     -   n2 on each occurrence, identically or differently, is 0, 1 or 2,         and     -   n3 is 1, 2 or 3, and     -   r is 0, 1, 2, 3 or 4.

Particular preference is given to dopants selected from the group consisting of the compounds of the following formulae:

-   -   in which     -   m is, on each occurrence, identically or differently, an integer         from 1 to 9 and     -   n is, on each occurrence, identically or differently, an integer         from 2 to 9.

Particularly preferred compounds of formula A are compounds of formula A-III.

Further preferred dopants are derivatives of the isosorbide, isomannitol or isoiditol of the following formula A-IV:

-   -   in which the group

-   -    is

-   -   preferably dianhydrosorbitol,     -   and chiral ethane diols, such as, for example,         diphenylethanediol (hydrobenzoin), in particular mesogenic         hydrobenzoin derivatives of the following formula A-V:

-   -   including the (S,S) enantiomers, which are not shown,     -   in which

-   -   -   are each, independently of one another, 1,4-phenylene, which             may also be mono-, di- or trisubstituted by L, or             1,4-cyclohexylene,

    -   L is H, F, Cl, CN or optionally halogenated alkyl, alkoxy,         alkylcarbonyl, alkoxycarbonyl or alkoxycarbonyloxy having 1-7         carbon atoms,

    -   c is 0 or 1,

    -   X is CH₂ or —C(O)—,

    -   Z⁰ is —COO—, —OCO—, —CH₂CH₂— or a single bond, and

    -   R⁰ is alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl or         alkylcarbonyloxy having 1-12 carbon atoms.

Examples of compounds of formula IV are:

The compounds of the formula A-IV are described in WO 98/00428. The compounds of the formula A-V are described in GB-A-2,328,207.

Very particularly preferred dopants are chiral binaphthyl derivatives, as described in WO 02/94805, chiral binaphthol acetal derivatives, as described in WO 02/34739, chiral TADDOL derivatives, as described in WO 02/06265, and chiral dopants having at least one fluorinated bridging group and a terminal or central chiral group, as described in WO 02/06196 and WO 02/06195.

Particular preference is given to chiral compounds of the formula A-VI

-   -   in which     -   X¹, X², Y¹ and Y² are each, independently of one another, F, Cl,         Br, I, CN, SCN, SF₅, straight-chain or branched alkyl having         from 1 to 25 carbon atoms, which is unsubstituted or         monosubstituted or polysubstituted by F, Cl, Br, I or CN and in         which, in addition, one or more non-adjacent CH₂ groups may         each, independently of one another, be replaced by —O—, —S—,         —NH—,     -    NR^(x)—, —CO—, —COO—, —OCO—, —OCOO—, —S—CO—, —CO—S—, —CH═CH— or         —C≡C— in such a way that O and/or S atoms are not bonded         directly to one another, a polymerisable group or cycloalkyl or         aryl having up to 20 carbon atoms, which may optionally be         monosubstituted or polysubstituted by halogen, preferably F, or         by a polymerisable group,     -   x¹ and x² are each, independently of one another, 0, 1 or 2,     -   y¹ and y² are each, independently of one another, 0, 1, 2, 3 or         4,     -   B¹ and B² are each, independently of one another, an aromatic or         partially or fully saturated aliphatic six-membered ring in         which one or more CH groups may each be replaced by N and one or         more non-adjacent CH₂ groups may each be replaced by O or S,     -   W¹ and W² are each, independently of one another,         —Z¹-A¹-(Z²-A²)_(m)-R, and one of the two is alternatively R¹ or         A³, but both are not simultaneously H, or

-   -   -   is

-   -   U¹ and U² are each, independently of one another, CH₂, O, S, CO         or CS,     -   V¹ and V² are each, independently of one another, (CH₂)_(n), in         which from one to four non-adjacent CH₂ groups may each be         replaced by O or S, and one of V¹ and V² and, in the case where

-   -   -   is

-   -   -   both are a single bond,

    -   n is 1, 2 or 3

    -   Z¹ and Z² are each, independently of one another, —O—, —S—,         —CO—, —COO—, —OCO—, —O—COO—, —CO—NR^(x)—, —NR^(x)—CO—, —O—CH₂—,         —CH₂—O—, —S—CH₂—, —CH₂—S—, —CF₂—O—, —O—CF₂—, —CF₂—S—, —S—CF₂—,         —CH₂—CH₂—, —CF₂—CH₂—, —CH₂—CF₂—, —CF₂—CF₂—, —CH═N—, —N═CH—,         —N═N—, —CH═CH—, —CF═CH—, —CH═CF—, —CF═CF—, —C≡C—, a combination         of two of these groups, where no two O and/or S and/or N atoms         are bonded directly to one another, preferably —CH═CH—COO—, or         —COO—CH═CH—, or a single bond,

    -   R^(x) denotes alkyl having 1 to 6 C atoms,

    -   A¹, A² and A³ are each, independently of one another,         1,4-phenylene, in which one or two non-adjacent CH groups may         each be replaced by N, 1,4-cyclohexylene, in which one or two         non-adjacent CH₂ groups may each be replaced by O or S,         1,3-dioxolane-4,5-diyl, 1,4-cyclohexenylene,         1,4-bicyclo[2.2.2]octylene, piperidine-1,4-diyl,         naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl or         1,2,3,4-tetrahydronaphthalene-2,6-diyl, where each of these         groups may be monosubstituted or polysubstituted by L, and in         addition A¹ can be a single bond,

    -   L is a halogen atom, preferably F, CN, NO₂, alkyl, alkoxy,         alkylcarbonyl, alkoxycarbonyl or alkoxycarbonyloxy having 1-7         carbon atoms, in which one or more H atoms may each be replaced         by F or Cl,

    -   m is in each case, independently, 0, 1, 2 or 3, and

    -   R and R¹ are each, independently of one another, H, F, Cl, Br,         I, CN, SCN, SF₅, straight-chain or branched alkyl having from 1         or 3 to 25 carbon atoms respectively, which may optionally be         monosubstituted or polysubstituted by F, Cl, Br, I or CN, and in         which one or more non-adjacent CH₂ groups may each be replaced         by —O—, —S—, —NH—, —NR⁰—, —CO—, —COO—, —OCO—, —O—COO—, —S—CO—,         —CO—S—, —CH═CH— or —C≡C—, where no two O and/or S atoms are         bonded directly to one another, or a polymerisable group.

Particular preference is given to chiral binaphthyl derivatives of the formula A-VI-1

-   -   in which ring B, R⁰ and Z⁰ are as defined for the formulae A-IV         and A-V, and b is 0, 1, or 2,     -   in particular those selected from the following formulae A-VI-1a         to A-VI-1c:

-   -   in which ring B, R⁰, and Z⁰ are as defined for the formula         A-VI-1, and     -   R⁰ as defined for formula A-IV or H or alkyl having from 1 to 4         carbon atoms, and     -   b is 0, 1 or 2,     -   and Z⁰ is, in particular, —OC(O)— or a single bond.

The concentration of the one or more chiral dopant(s), in the LC medium is preferably in the range from 0.001% to 20%, preferably from 0.05% to 5%, more preferably from 0.1% to 2%, and, most preferably from 0.5% to 1.5%. These preferred concentration ranges apply in particular to the chiral dopant S-4011 or R-4011 (both from Merck KGaA) and for chiral dopants having the same or a similar HTP. For Chiral dopants having either a higher or a lower absolute value of the HTP compared to S-4011 these preferred concentrations have to be decreased, respectively increased proportionally according to the ratio of their HTP values relatively to that of S-4011.

The pitch p of the LC media or host mixtures according to the invention is preferably in the range of from 5 to 50 μm, more preferably from 8 to 30 μm and particularly preferably from 10 to 20 μm.

Preferably, the media according to the invention, comprise a stabilizer selected from the group of compounds of the formulae ST-1 to ST-18.

-   -   in which     -   R^(ST) denotes H, an alkyl or alkoxy radical having 1 to 15 C         atoms, where, in addition, one or more CH₂ groups in these         radicals may each be replaced, independently of one another, by         —C≡C—, —CF₂O—, —OCF₂—, —CH═CH—,

-   -    —O—, —CO—O—, —O—CO— in such a way that O atoms are not linked         directly to one another, and in which, in addition, one or more         H atoms may be replaced by halogen,

-   -   -   denotes

-   -   Z^(ST) each, independently of one another, denote —CO—O—,         —O—CO—, —CF₂O—, —OCF₂—, —CH₂O—, —OCH₂—, —CH₂—, —CH₂CH₂—,         —(CH₂)₄—, —CH═CH—CH₂O—, —C₂F₄—, —CH₂CF₂—, —CF₂CH₂—, —CF═CF—,         —CH═CF—, —CF═CH—, —CH═CH—, —C≡C— or a single bond,     -   L¹ and L² each, independently of one another, denote F, Cl, CF₃         or CHF₂,     -   p denotes 1 or 2, and     -   q denotes 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10.

Of the compounds of the formula ST, special preference is given to the compounds of the formulae

-   -   in which n=1, 2, 3, 4, 5, 6 or 7, preferably n=1 or 7

-   -   in which n=1, 2, 3, 4, 5, 6 or 7, preferably n=3

-   -   in which n=1, 2, 3, 4, 5, 6 or 7, preferably n=3

In the compounds of the formulae ST-3a and ST-3b, n preferably denotes 3. In the compounds of the formula ST-2a, n preferably denotes 7.

Very particularly preferred mixtures according to the invention comprise one or more stabilizers from the group of the compounds of the formulae ST-2a-1, ST-3a-1, ST-3b-1, ST-8-1, ST-9-1 and ST-12:

The compounds of the formulae ST-1 to ST-18 are preferably each present in the liquid-crystal mixtures according to the invention in amounts of 0.005-0.5%, based on the mixture.

If the mixtures according to the invention comprise two or more compounds from the group of the compounds of the formulae ST-1 to ST-18, the concentration correspondingly increases to 0.01-1% in the case of two compounds, based on the mixtures.

However, the total proportion of the compounds of the formulae ST-1 to ST-18, based on the mixture according to the invention, should not exceed 2%.

Other mesogenic compounds which are not explicitly mentioned above can optionally and advantageously also be used in the media in accordance with the present invention. Such compounds are known to the person skilled in the art.

In a preferred embodiment of the present invention, the total concentration of compounds of formula C in the liquid-crystalline medium is 5% or more, preferably 8% or more, very preferably 10% or more and particularly preferably 12% or more.

In a preferred embodiment of the present invention, the liquid-crystalline media preferably comprise in total 2% to 40%, preferably 5% to 30% and particularly preferably 8% to 25% of compounds of formula C.

In a preferred embodiment of the present invention, the liquid-crystalline media comprise in total 5% to 45%, preferably 10% to 40% and particularly preferably 15% to 35% of one or more compounds of formula T, preferably selected from the formulae T-1a and T-2a, very preferably from T-1a-5 and T-2a-4.

In a preferred embodiment of the present invention, the liquid-crystalline media comprise in total 5% to 35%, preferably 10% to 30% and particularly preferably 15% to 25% of one or more compounds of the formula T-1a.

In a preferred embodiment of the present invention, the liquid-crystalline media comprise in total 5% to 35%, preferably 10% to 30% and particularly preferably 15% to 25% of one or more compounds of the formula T-1a, and in addition 5 to 15% of one or more compounds of the formula T-2a-4.

In a preferred embodiment, the medium comprises one or more compounds of formula I, preferably of formula I-2 or I-3, in a total concentration in the range of from 1% to 25%, more preferably from 2% to 20%, and particularly preferably from 5% to 15%.

In a preferred embodiment of the present invention the medium comprises one or more compounds of formula II, preferably of formula II-1, in a total concentration of 5% to 35%, more preferably 10% to 30%, particularly preferably 15% to 25%.

In a preferred embodiment of the present invention the medium comprises one or more compounds of formula IIA-1 in a total concentration of 5% to 25%, more preferably 8% to 20%, particularly preferably 12% to 17%.

In a preferred embodiment of the present invention the medium comprises one or more compounds of formula II-1 in an total concentration of 30% or less, more preferably 25% or less, particularly preferably 20% or less.

In a preferred embodiment of the present invention the medium comprises one or more compounds of formula III, preferably III-1 and/or III-2, more preferably III-1h and/or III-1b, in a total concentration of 15% to 70%, more preferably 25% to 60%, particularly preferably 35% to 50%.

In a preferred embodiment, the medium comprises one or more compounds of the formulae C and I and II and/or IIA, and III and T, preferably in a total concentration of 90% or more, more preferably 95%, 96% or 97% or more, very preferably 98% or more and in particular 99% or more.

In a preferred embodiment, the medium comprises one or more compounds of the formulae C and II and III and T, preferably in a total concentration of 90% or more, more preferably 95%, 96% or 97% or more, very preferably 98% or more and in particular 99% or more.

In a preferred embodiment, the medium comprises one or more compounds of the formulae C and I and III and T, preferably in a total concentration of 90% or more, more preferably 95%, 96% or 97% or more, very preferably 98% or more and in particular 99% or more.

Further preferred embodiments of the present invention, taken alone or in combination with one another, are as follows, wherein some compounds are abbreviated using the acronyms given in Table C below:

-   -   The medium comprises one, two, three, four or more compounds of         formula III-1, preferably selected from the compounds of the         formulae III-1b, III-1f and III-1h; more preferably of III-1b         and III-1h;     -   The medium comprises a compound of formula III-1b, preferably in         a total concentration in the range of from 5% to 35%, more         preferably 10% to 30%, in particular 15% to 25%;     -   The medium comprises a compound of formula III-1h, preferably in         a total concentration in the range of from 10% to 40%, more         preferably 15% to 35%, in particular 18% to 30%;     -   The medium comprises the compound PPU-TO-S and/or PPTU-TO-S         and/or PTPU-TO-S and/or PP(1)TO-n-S;     -   The medium comprises one or more compounds of formula I-2d,         preferably the compounds PGU-2-S and/or PGU-3-S and/or PGU-4-S,         and/or CPU-2-S and/or CPU-3-S and/or CPU-4-S;     -   The medium comprises one or more compounds of formula I-2d and         formula II-1b, preferably the compounds PGU-3-S and/or PGU-4-S         and PTU-3-S and/or PTU-4-S and/or PTU-5-S;     -   The medium comprises one or more compounds of formula PPTU-n-S         and/or PTPU-n-S in an total concentration in the range of from         15 to 25%;     -   The medium comprises one or more compounds of formula PPTU-n-S         and/or PTPU-n-S and/or PGTU-n-S in a total concentration in the         range of from 15 to 30%, in which n is 1, 2, 3, 4, 5, or 6;     -   The medium comprises one or more compounds of formula ST-3,         preferably ST-3a and/or ST-3b, particularly preferably ST-3b-1,         in a total concentration in the range of from 0.01 to 1%,         preferably from 0.05 to 0.5%, particularly from 0.10 to 0.15%.

The liquid-crystal media in accordance with the present invention preferably have a clearing point of 90° C. or more, more preferably 100° C. or more, more preferably 110° C. or more, more preferably 120° C. or more, more preferably 130° C. or more, particularly preferably 140° C. or more and very particularly preferably 150° C. or more.

The liquid-crystal media in accordance with the present invention preferably have a clearing point of 160° C. or less, more preferably 140° C. or less, particularly preferably 120° C. or less, and very particularly preferably 100° C. or less.

The nematic phase of the media according to the invention preferably extends at least from 0° C. or less to 90° C. or more. It is advantageous for the media according to the invention to exhibit even broader nematic phase ranges, preferably at least from −10° C. or less to 120° C. or more, very preferably at least from −20° C. or less to 140° C. or more and in particular at least from −30° C. or less to 150° C. or more, very particularly preferably at least from −40° C. or less to 170° C. or more.

The Δε of the liquid-crystal medium according to the present invention, at 1 kHz and 20° C., is preferably 5 or more, more preferably 7 or more and very preferably 10 or more.

The birefringence (Δn) of the liquid-crystal media according to the present invention, at 589 nm (Na^(D)) and 20° C., is preferably 0.280 or more, more preferably 0.300 or more, even more preferably 0.320 or more, very preferably 0.330 or more and in particular 0.350 or more.

The Δn of the liquid-crystal media according to the present invention, at 589 nm (Na^(D)) and 20° C., is preferably in the range from 0.200 to 0.900, more preferably in the range from 0.250 to 0.800, even more preferably in the range from 0.300 to 0.700 and very particularly preferably in the range from 0.350 to 0.600.

In a preferred embodiment of the present application, the Δn of the liquid-crystal media in accordance with the present invention is preferably 0.50 or more, more preferably 0.55 or more.

The compounds of the formulae I to III in each case include dielectrically positive compounds having a dielectric anisotropy of greater than 3, dielectrically neutral compounds having a dielectric anisotropy of less than 3 and greater than −1.5 and dielectrically negative compounds having a dielectric anisotropy of −1.5 or less.

The compounds of the formulae C, I, II and III are preferably dielectrically positive.

In the present application, the expression dielectrically positive describes compounds or components where Δε>3.0, dielectrically neutral describes those where −1.5≤Δε≤3.0 and dielectrically negative describes those where Δε<−1.5. Δε is determined at a frequency of 1 kHz and at 20° C. The dielectric anisotropy of the respective compound is determined from the results of a solution of 10% of the respective individual compound in a nematic host mixture. If the solubility of the respective compound in the host mixture is less than 10%, the concentration is reduced to 5%. The capacitances of the test mixtures are determined both in a cell having homeotropic alignment and in a cell having homogeneous alignment. The cell thickness of both types of cells is approximately 20 μm. The voltage applied is a rectangular wave having a frequency of 1 kHz and an effective value of typically 0.5 V to 1.0 V, but it is always selected to be below the capacitive threshold of the respective test mixture.

Δε is defined as (ε_(∥)−ε_(⊥)), while ε_(ave.) is (ε_(∥)+2ε_(⊥))/3.

The host mixture used for the determination of physical constants of pure compounds by extrapolation is ZLI-4792 from Merck KGaA, Germany. The absolute values of the dielectric constants, the birefringence (Δn) and the rotational viscosity (γ₁) of the compounds are determined from the change in the respective values of the host mixture on addition of the compounds. The concentration in the host is 10% or in case of insufficient solubility 5%. The values are extrapolated to a concentration of 100% of the added compounds.

In the examples, the phase sequences of pure compounds are given using the following abbreviations:

-   -   K: crystalline, N: nematic, SmA: smectic A, SmB: smectic B, I:         isotropic.

Components having a nematic phase at the measurement temperature of 20° C. are measured as such, all others are treated like compounds.

The expression threshold voltage in the present application refers to the optical threshold and is quoted for 10% relative contrast (V₁₀), and the expression saturation voltage refers to the optical saturation and is quoted for 90% relative contrast (V₉₀), in both cases unless expressly stated otherwise. The capacitive threshold voltage (V₀), also called the Fredericks threshold (V_(Fr)), is only used if expressly mentioned.

The parameter ranges indicated in this application all include the limit values, unless expressly stated otherwise.

The different upper and lower limit values indicated for various ranges of properties in combination with one another give rise to additional preferred ranges.

Throughout this application, the following conditions and definitions apply, unless expressly stated otherwise. All concentrations are quoted in percent by weight and relate to the respective mixture as a whole, all temperatures are quoted in degrees Celsius and all temperature differences are quoted in differential degrees. All physical properties are determined in accordance with “Merck Liquid Crystals, Physical Properties of Liquid Crystals”, Status November 1997, Merck KGaA, Germany, and are quoted for a temperature of 20° C., unless expressly stated otherwise. The optical anisotropy (Δn) is determined at a wavelength of 589.3 nm. The dielectric anisotropy (Δε) is determined at a frequency of 1 kHz. The threshold voltages, as well as all other electro-optical properties, are determined using test cells produced at Merck KGaA, Germany. The test cells for the determination of Δε have a cell thickness of approximately 20 μm. The electrode is a circular ITO electrode having an area of 1.13 cm² and a guard ring. The orientation layers are SE-1211 from Nissan Chemicals, Japan, for homeotropic orientation (ε_(∥)) and polyimide AL-1054 from Japan Synthetic Rubber, Japan, for homogeneous orientation (ε_(⊥)). The capacitances are determined using a Solatron 1260 frequency response analyser using a sine wave with a voltage of 0.3 V_(rms). The light used in the electro-optical measurements is white light. A set-up using a commercially available DMS instrument from Autronic-Melchers, Germany, is used here. The characteristic voltages have been determined under perpendicular observation. The threshold (V₁₀), mid-grey (V₅₀) and saturation (V₉₀) voltages have been determined for 10%, 50% and 90% relative contrast, respectively.

The liquid-crystalline media are investigated with respect to their properties in the microwave frequency range as described in A. Penirschke et al. “Cavity Perturbation Method for Characterization of Liquid Crystals up to 35 GHz”, 34^(th) European Microwave Conference—Amsterdam, pp. 545-548. Compare in this respect also A. Gaebler et al. “Direct Simulation of Material Permittivities . . . ”, 12MTC 2009—International Instrumentation and Measurement Technology Conference, Singapore, 2009 (IEEE), pp. 463-467, and DE 10 2004 029 429 A, in which a measurement method is likewise described in detail.

The liquid crystal is introduced into a polytetrafluoroethylene (PTFE) or quartz capillary. The capillary has an inner diameter of 0.5 mm and an outer diameter of 0.78 mm. The effective length is 2.0 cm. The filled capillary is introduced into the center of the cylindrical cavity with a resonance frequency of 19 GHz. This cavity has a length of 11.5 mm and a radius of 6 mm. The input signal (source) is then applied, and the frequency depending response of the cavity is recorded using a commercial vector network analyzer (N5227A PNA Microwave Network Analyzer, Keysight Technologies Inc. USA. For other frequencies, the dimensions of the cavity are adapted correspondingly.

The change in the resonance frequency and the Q factor between the measurement with the capillary filled with the liquid crystal and the measurement without the capillary filled with the liquid crystal is used to determine the dielectric constant and the loss angle at the corresponding target frequency by means of equations 10 and 11 in the above-mentioned publication A. Penirschke et al., 34^(th) European Microwave Conference—Amsterdam, pp. 545-548, as described therein.

The values for the components of the properties perpendicular and parallel to the director of the liquid crystal are obtained by alignment of the liquid crystal in a magnetic field. To this end, the magnetic field of a permanent magnet is used. The strength of the magnetic field is 0.35 tesla.

Preferred components are phase shifters, varactors, wireless and radio wave antenna arrays, matching circuit adaptive filters and others.

In the present application, the term compounds is taken to mean both one compound and a plurality of compounds, unless expressly stated otherwise.

All mixtures according to the invention are nematic. The liquid-crystal media according to the invention preferably have nematic phases in preferred ranges given above. The expression have a nematic phase here means on the one hand that no smectic phase and no crystallization are observed at low temperatures at the corresponding temperature and on the other hand that no clearing occurs on heating from the nematic phase. At high temperatures, the clearing point is measured in capillaries by conventional methods. The investigation at low temperatures is carried out in a flow viscometer at the corresponding temperature and checked by storage of bulk samples: The storage stability in the bulk (LTS) of the media according to the invention at a given temperature T is determined by visual inspection. 2 g of the media of interest are filled into a closed glass vessel (bottle) of appropriate size placed in a refrigerator at a predetermined temperature. The bottles are checked at defined time intervals for the occurrence of smectic phases or crystallization. For every material and at each temperature two bottles are stored. If crystallization or the appearance of a smectic phase is observed in at least one of the two correspondent bottles the test is terminated and the time of the last inspection before the one at which the occurrence of a higher ordered phase is observed is recorded as the respective storage stability. The test is finally terminated after 1000 h, i.e an LTS value of 1000 h means that the mixture is stable at the given temperature for at least 1000 h.

The liquid crystals employed preferably have a positive dielectric anisotropy. This is preferably 2 or more, preferably 4 or more, particularly preferably 6 or more and very particularly preferably 10 or more.

Furthermore, the liquid-crystal media according to the invention are characterized by high anisotropy values in the microwave range. The birefringence at about 19 GHz is, for example, preferably 0.14 or more, particularly preferably 0.15 or more, particularly preferably 0.20 or more, particularly preferably 0.25 or more and very particularly preferably 0.30 or more. In addition, the birefringence is preferably 0.80 or less.

The dielectric anisotropy in the microwave range is defined as Δε_(r)≡(ε_(r,∥)−ε_(r,⊥))

The tunability (τ) is defined as τ≡(Δε_(r)/ε_(r,∥)).

The material quality (η) is defined as η≡(τ/tan δ_(εr,max.)), where

the maximum dielectric loss is tan δ_(εr,max.)≡max.{tan δ_(εr,⊥);tan δ_(εr,∥)}.

The tunability τ of the medium according to the invention, measured at 20° C. and 19 GHz is 0.250 or more, preferably 0.300 or more, 0.310 or more, 0.320 or more, 0.330 or more, or 0.340 or more, very preferably 0.345 or more and in particular 0.350 or more.

The material quality (η) of the preferred liquid-crystal materials is 6 or more, preferably 8 or more, preferably 10 or more, preferably 15 or more, preferably 17 or more, preferably 20 or more, particularly preferably 25 or more and very particularly preferably 30 or more.

In the corresponding components, the preferred liquid-crystal materials have phase shifter qualities of 15°/dB or more, preferably 20°/dB or more, preferably 30°/dB or more, preferably 40°/dB or more, preferably 50°/dB or more, particularly preferably 80°/dB or more and very particularly preferably 100°/dB or more.

In some embodiments, however, liquid crystals having a negative value of the dielectric anisotropy can also advantageously be used.

The liquid crystals employed are either individual substances or mixtures. They preferably have a nematic phase.

The liquid-crystal media in accordance with the present invention may comprise further additives and chiral dopants in the usual concentrations. The total concentration of these further constituents is in the range from 0% to 10%, preferably 0.1% to 6%, based on the mixture as a whole. The concentrations of the individual compounds used are each preferably in the range from 0.1% to 3%. The concentration of these and similar additives is not taken into consideration when quoting the values and concentration ranges of the liquid-crystal components and liquid-crystal compounds of the liquid-crystal media in this application.

Preferably the media according to the present invention comprise one or more chiral compounds as chiral dopants in order to adjust their cholesteric pitch. Their total concentration in the media according to the instant invention is preferably in the range 0.05% to 15%, more preferably from 1% to 10% and most preferably from 2% to 6%.

Optionally the media according to the present invention may comprise further liquid crystal compounds in order to adjust the physical properties. Such compounds are known to the skilled person. Their concentration in the media according to the instant invention is preferably 0% to 30%, more preferably 0.1% to 20% and most preferably 1% to 15%.

The response times are given as rise time (τ_(on)) for the time for the change of the relative tuning, respectively of the relative contrast for the electro-optical response, from 0% to 90% (t₉₀−t₀), i.e. including the delay time (t₁₀−t₀), as decay time (τ_(off)) for the time for the change of the relative tuning, respectively of the relative contrast for the electro-optical response, from 100% back to 10% (t₁₀₀−t₁₀) and as the total response time (τ_(total)=τ_(on)+τ_(off)), respectively.

The liquid-crystal media according to the invention consist of a plurality of compounds, preferably 3 to 30, more preferably 4 to 20 and very preferably 4 to 16 compounds. These compounds are mixed in a conventional manner. In general, the desired amount of the compound used in the smaller amount is dissolved in the compound used in the larger amount. If the temperature is above the clearing point of the compound used in the higher concentration, it is particularly easy to observe completion of the dissolution process. It is, however, also possible to prepare the media in other conventional ways, for example using so-called pre-mixes, which can be, for example, homologous or eutectic mixtures of compounds, or using so-called “multi-bottle” systems, the constituents of which are themselves ready-to-use mixtures.

All temperatures, such as, for example, the melting point T(C,N) or T(C,S), the transition from the smectic (S) to the nematic (N) phase T(S,N) and the clearing point T(N,I) of the liquid crystals, are quoted in degrees Celsius. All temperature differences are quoted in differential degrees.

In the present invention and especially in the following examples, the structures of the mesogenic compounds are indicated by means of abbreviations, also referred to as acronyms. In these acronyms, the chemical formulae are abbreviated as follows using Tables A to D below. All groups C_(n)H_(2n+1), C_(m)H_(2m+1) and C_(l)H_(2l+1), and C_(n)H_(2n), C_(m)H_(2m) and C_(l)H_(2l) denote straight-chain alkyl or alkylene, respectively, in each case having n, m or l C atoms, wherein n and m, independently are 1, 2, 3, 4, 5, 6 or 7 and l is 1, 2 or 3. Table A lists the codes used for the ring elements of the core structures of the compounds, while Table B shows the linking groups. Table C gives the meanings of the codes for the left-hand or right-hand end groups. Table D shows illustrative structures of compounds with their respective abbreviations.

TABLE A Ring elements C

D

Dl

A

Al

G

Gl

G(Cl)

P(Cl,Cl)

U

Ul

U(F,F)

Y

M

Ml

N

Nl

Np

N3f

N3fl

tH

tHl

tH2f

tH2fl

dH

K

Kl

L

Ll

F

Fl

P

P(n,m)

P(o)

Pl(o)

P(i3)

Pl(ic3)

P(t4)

Pl(t4)

P(c3)

Pl(c3)

P(c4)

Pl(c4)

P(c5)

Pl(c5)

P(e5)

Pl(e5)

P(c6)

Pl(c6)

P(e6)

Pl(e6)

Gl(o)

  in which o = 1, 2, 3, 4, 5 or 6 G(o)

  in which o = 1, 2, 3, 4, 5 or 6 Gl(i3)

G(i3)

Gl(t4)

G(t4)

Gl(c3)

G(c3)

Gl(c4)

G(c4)

Gl(c5)

G(c5)

Gl(e5)

G(e5)

Gl(c6)

G(c6)

Gl(e6)

G(e6)

Np(1,4)

Th

TABLE B Linking groups E —CH₂CH₂— Z —CO—O— V —CH═CH— ZI —O—CO— X —CF═CH— O —CH₂—O— XI —CH═CF— OI —O—CH₂— B —CF═CF— Q —CF₂—O— T —C≡C— QI —O—CF₂— W —CF₂CF₂— End groups Left-hand side Right-hand side Used alone -n- C_(n)H_(2n+1)— -n —C_(n)H_(2n+1) -nO- C_(n)H_(2n+1)—O— -On —O—C_(n)H_(2n+1) -V- CH₂═CH— -V —CH═CH₂ -nV- C_(n)H_(2n+1)—CH═CH— -nV —C_(n)H_(2n)—CH═CH₂ -Vn- CH₂═CH—C_(n)H_(2n+1)— -Vn —CH═CH—C_(n)H_(2n+1) -nVm- C_(n)H_(2n+1)—CH═CH—C_(m)H_(2m)— -nVm —C_(n)H_(2n)—CH═CH—C_(m)H_(2m+1) -N- N≡C— -N —C≡N -S- S═C═N— -S —N═C═S -F- F— -F —F -CL- Cl— -CL —Cl -M- CFH₂— -M —CFH₂ -D- CF₂H— -D —CF₂H -T- CF₃— -T —CF₃ -MO- CFH₂O— -OM —OCFH₂ -DO- CF₂HO— -OD —OCF₂H -TO- CF₃O— -OT —OCF₃ -FXO- CF₂═CH—O— -OXF —O—CH═CF₂ -A- H—C≡C— -A —C≡C—H -nA- C_(n)H_(2n+1)—C≡C— -An —C≡C—C_(n)H_(2n+1) -NA- N≡C—C≡C— -AN —C≡C—C≡N Used in combination with others - . . . A . . . - —C≡C— - . . . A . . . —C≡C— - . . . V . . . - —CH═CH— - . . . V . . . —CH═CH— - . . . Z . . . - —CO—O— - . . . Z . . . —CO—O— - . . . ZI . . . - —O—CO— - . . . ZI . . . —O—CO— - . . . K . . . - —CO— - . . . K . . . —CO— - . . . W . . . - —CF═CF— - . . . W . . . —CF═CF— in which n and m each denote integers, and the three dots “. . .” are placeholders for other abbreviations from this table.

The following table shows illustrative structures together with their respective abbreviations. These are shown in order to illustrate the meaning of the rules for the abbreviations. They furthermore represent compounds which are preferably used.

TABLE C Illustrative structures

in which m and n, identically or differnetly, are 1, 2, 3, 4, 5, 6 or 7.

The following illustrative structures are compounds, which are preferably additionally used in the media:

Preferably, the medium according to the invention comprises one or more compounds selected from the compounds of Table C.

The following table, Table D, shows illustrative compounds which can be used as alternative stabilizers in the mesogenic media in accordance with the present invention. The total concentration of these and similar compounds in the media is preferably 5% or less.

TABLE D

In a preferred embodiment of the present invention, the mesogenic media comprise one or more compounds selected from the group of the compounds from Table D.

The following table, Table E, shows illustrative compounds which can preferably be used as chiral dopants in the mesogenic media in accordance with the present invention.

TABLE E

In a preferred embodiment of the present invention, the mesogenic media comprise one or more compounds selected from the group of the compounds of Table E.

The mesogenic media in accordance with the present application preferably comprise two or more, preferably four or more, compounds selected from the group consisting of the compounds from the above tables.

EXAMPLES

The following examples illustrate the present invention without limiting it in any way. It is clear to the person skilled in the art from the physical properties what properties can be achieved and in what ranges they can be modified. In particular, the combination of the various properties which can preferably be achieved is thus well defined for the person skilled in the art.

Synthesis Examples Abbreviations

-   -   RT room temperature (typically 20° C.±1° C.)     -   THF Tetrahydrofuran     -   MTB ether Methyl-tert-butyl ether     -   DCM Dichloromethane     -   dist. distilled     -   XPhos 2-Dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl     -   XPhos Pd G2         Chloro(2-dicyclohexylphosphino-2′,4′,6′-triisopropyl-1,1′-biphenyl)[2-(2′-amino-1,1′-biphenyl)palladium         (II)

Example 1: 5-[4-(4-Butylphenyl)phenyl]ethynyl]-1-chloro-3-fluoro-2-isothiocyanato-benzene Step 1: [4-(4-Butylphenyl)phenyl]ethynyl-trimethyl-silane

A mixture of 1-bromo-4-(4-butylphenyl)benzene (CAS 63619-54-5, 33.5 g, 116 mmol), triethylamine (135 ml), bis(triphenylphosphine)-palladium(II)-chloride (3.2 g, 4.6 mmol), copper(I)-iodide (530 mg, 2.8 mmol) and trimethylsilyl acetylene (33.6 ml, 237 mmol) is heated at reflux temperature overnight. Then water and MTB-ether are added to the reaction mixture. The phases are separated, and the aqueous layer is extracted with MTB-ether. The combined organic phases are washed with dist. water, dried (sodium sulfate) and concentrated i. vac. The residue is purified by flash chromatography (heptane) to give [4-(4-butylphenyl)phenyl]ethynyl-trimethyl-silane as an orange solid.

Step 2: 1-Butyl-4-(4-ethynylphenyl)benzene

Tetra-n-butylammonium fluoride (113 ml, 1 M in THF) is added slowly to a solution of [4-(4-butylphenyl)phenyl]ethynyl-trimethyl-silane (34.6 g, 113 mmol) in THF (650 ml) at 10° C. The reaction mixture is stirred at RT overnight. Then water, hydrochloric acid (1 M) and MTB-ether are added. The phases are separated, and the aqueous phase is extracted with MTB-ether. The combined organic phases are washed with brine, dried (sodium sulfate) and concentrated in vacuo. The residue is purified by flash chromatography (heptane) to give 1-butyl-4-(4-ethynylphenyl)benzene as a light yellow solid.

Step 3: 4-[4-(4-Butylphenyl)phenylethynyl]-2-chloro-6-fluoro-aniline

A mixture of 1-butyl-4-(4-ethynylphenyl)benzene (4.0 g, 17 mmol) and 4-bromo-2-chloro-6-fluoro-aniline (3.9 g, 17 mmol) in diisopropylamine (40 ml) and THF (40 ml) is heated to 70° C. under nitrogen atmosphere. Then XPhos PD G2 (27 mg, 0.03 mmol), XPhos (16 mg, 0.03 mmol) and copper(I)-iodide (3.3 mg, 0.02 mmol) are added, and the reaction mixture is stirred at 70° C. overnight. Then it is filtered and concentrated in vacuo. The residue is purified by flash chromatography (heptane and heptane/MTB-ether) to give 4-[4-(4-butylphenyl)phenylethynyl]-2-chloro-6-fluoro-aniline as a light brown solid.

Step 4: 5-[4-(4-Butylphenyl)phenyl]ethynyl]-1-chloro-3-fluoro-2-isothiocyanato-benzene

Thiophosgene (1.5 ml, 19 mmol) is added dropwise to a mixture of 4-[4-(4-butylphenyl)phenylethynyl]-2-chloro-6-fluoro-aniline (6.6 g, 18 mmol) and 1,4 diazabicyclo[2.2.2]octane (4.9 g, 44 mmol) in dichloromethane (70 ml) at 0° C., and the reaction mixture is stirred for 1 h at room temperature. The reaction is hydrolyzed with brine, and the phases are separated. The aqueous phase is extracted with dichloromethane, and the combined organic phases are dried (sodium sulfate) and concentrated in vacuo. The residue is purified by flash chromatography (heptane) and crystallization with heptane and acetone to give 5-[4-(4-butylphenyl)phenyl]ethynyl]-1-chloro-3-fluoro-2-isothiocyanato-benzene as a pale yellow powder.

Phase sequence K 51 N 171 I.

-   -   Δε=17.2     -   Δn=0.4564     -   γ₁=911 mPas

In analogy to Synthesis Example 1 the following compounds are obtained:

physical No. Compound parameters 2

3

4

5

6

7

8

9

10

K 42 I Δε = 16.9 Δn = 0.3234 γ₁ = 104 mPas 11

12

13

14

15

K 62 I Δε = 3.8 Δn = 0.2595 γ₁ = 163 mPas 16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

K 85 N 173.0 I Δε = 17.6 Δn = 0.4423 46

47

48

49

K 98 N 121.8 I Δε = 5.9 Δn = 0.3909 50

51

K 122 N 177 I Δε = 2.5 Δn = 0.4123 γ₁ = 883 mPas 52

53

54

55

K 107 N 178 I Δε = 3.3 Δn = 0.4035 γ₁ = 771 mPas 56

57

58

59

60

61

62

63

64

65

K 77 I 66

K 58 I Δε = 14.2 Δn = 0.2480 γ₁ = 173 mPas 67

68

69

70

71

72

73

74

75

76

77

78

79

80

81

82

83

84

85

86

87

88

89

90

91

92

93

94

K 81 N 141.4 I 95

96

97

98

99

100

101

102

103

104

105

106

107

108

109

Mixture Examples

Liquid-crystal mixtures N1 to N5 having the compositions and properties as indicated in the following tables are prepared and characterized with respect to their general physical properties and their applicability in microwave components at 19 GHz and 20° C.

Example N1

PPTU-4-S 6.0 T(N, I) [° C.]: 154.5 PPTU-5-S 13.0 τ [20° C., 19 GHz]: 0.329 PPU-TO-S 22.0 ε_(r, ∥) [20° C., 19 GHz]: 3.67 PGU-3-S 12.0 ε_(r, ⊥) [20° C., 19 GHz]: 2.47 CPTU-5-S 24.0 tan δ_(ε r, ∥) [20° C., 19 GHz]: 0.0052 P(2)TU-5-S 15.0 tan δ_(ε r, ⊥) [20° C., 19 GHz]: 0.0090 PPTG(CI)-4-S 8.0 η [20° C., 19 GHz]: 36.6 Σ 100.0

Example N2

PPTU-4-S 6.0 T(N, I) [° C.]: 155.5 PPTU-5-S 12.0 Δε [1 kHz, 20° C.]: 18.1 PPU-TO-S 17.0 ε_(∥) [1 kHz, 20° C.]: 22.0 CPTU-5-S 20.0 ε_(⊥) [1 kHz, 20° C.]: 3.9 PTU-3-S 10.0 γ₁ [mPa s, 20° C.]: 595 PTU-5-S 10.0 K₁ [pN, 20° C.]: 18.2 PPTG(CI)-4-S 25.0 K₃ [pN, 20° C.]: 23.1 Σ 100.0 K₃/K₁ [pN, 20° C.]: 1.27 V₀ [V, 20° C.]: 1.05 τ [20° C., 19 GHz]: 0.341 ε_(r, ∥) [20° C., 19 GHz]: 3.74 ε_(r, ⊥) [20° C., 19 GHz]: 2.46 tan δ_(ε r, ∥) [20° C., 19 GHz]: 0.0051 tan δ_(ε r, ⊥) [20° C., 19 GHz]: 0.0087 η [20° C., 19 GHz]: 39.4

Example N3

PPTU-4-S 6.0 T(N, I) [° C.]: 163 PPTU-5-S 12.0 Δε [1 kHz, 20° C.]: 15.5 PPU-TO-S 23.0 ε_(∥) [1 kHz, 20° C.]: 19.3 PGU-3-S 10.0 ε_(⊥) [1 kHz, 20° C.]: 3.8 CPTU-5-S 25.0 γ₁ [mPa s, 20° C.]: 671 PP(1)TU-TO-S 10.0 K₁ [pN, 20° C.]: 16.2 PTG(CI)-4-S 14.0 K₃ [pN, 20° C.]: 27.7 Σ 100.0 K₃/K₁ [pN, 20° C.]: 1.70 V₀ [V, 20° C.]: 1.08 τ [20° C., 19 GHz]: 0.341 ε_(r, ∥) [20° C., 19 GHz]: 3.68 ε_(r, ⊥) [20° C., 19 GHz]: 2.42 tan δ_(ε r, ∥) [20° C., 19 GHz]: 0.0054 tan δ_(ε r, ⊥) [20° C., 19 GHz]: 0.0093 η [20° C., 19 GHz]: 36.7

Example N4

PPTU-4-S 6.0 Δε [1 kHz, 20° C.]: 14.4 PPTU-5-S 12.0 ε_(∥) [1 kHz, 20° C.]: 18.1 PPU-TO-S 23.0 ε_(⊥) [1 kHz, 20° C.]: 3.7 CPTU-5-S 25.0 γ₁ [mPa s, 20° C.]: 630 PTG(CI)-4-S 14.0 K₁ [pN, 20° C.]: 15.5 PP(1)TU-TO-S 10.0 K₃ [pN, 20° C.]: 27.0 CPU-2-S 10.0 K₃/K₁ [pN, 20° C.]: 1.74 Σ 100.0 V₀ [V, 20° C.]: 1.10 τ [20° C., 19 GHz]: 0.334 ε_(r, ∥) [20° C., 19 GHz]: 3.65 ε_(r, ⊥) [20° C., 19 GHz]: 2.43 tan δ_(ε r, ∥) [20° C., 19 GHz]: 0.0053 tan δ_(ε r, ⊥) [20° C., 19 GHz]: 0.0088 η [20° C., 19 GHz]: 37.9

Example N5

PTU-3-S 16.0 T(N, I) [° C.]: 169.5 PPTU-4-S 10.0 Δε [1 kHz, 20° C.]: 24.8 PPTU-5-S 20.0 ε_(r, ∥) [1 kHz, 20° C.]: 28.9 CPTU-5-S 24.0 ε_(r, ⊥) [1 kHz, 20° C.]: 4.1 PGTU-4-S 10.0 γ₁ [mPa s, 20° C.]: 536 PGU-3-S 10.0 K₁ [pN, 20° C.]: 21.7 PTPG(CI)-4-S 10.0 K₃ [pN, 20° C.]: 25.3 Σ 100.0 K₃/K₁ [pN, 20° C.]: 1.17 V₀ [V, 20° C.]: 0.98 LTS bulk [h, −20° C.]: 1000 LTS bulk [h, −30° C.]: 408 τ [20° C., 19 GHz]: 0.348 ε_(r, ∥) [20° C., 19 GHz]: 3.77 ε_(r, ⊥) [20° C., 19 GHz]: 2.46 tan δ_(ε r, ∥) [20° C., 19 GHz]: 0.0049 tan δ_(ε r, ⊥) [20° C., 19 GHz]: 0.0094 η [20° C., 19 GHz]: 37.2 

The invention claimed is:
 1. A compound of formula C

in which R^(C) denotes H, alkyl or alkoxy having 1 to 12 C atoms, or alkenyl, alkenyloxy or alkoxyalkyl having 2 to 12 C atoms, in which one or more CH₂-groups may be replaced by

 or denotes a group R^(P), R^(P) denotes halogen, CN, NCS, R^(F), R^(F)—O— or R^(F)—S—, wherein R^(F) denotes fluorinated alkyl having 1 to 9 C atoms or fluorinated alkenyl having 2 to 9 C atoms, Z^(C1), Z^(C2) identically or differently, denote —CH═CH—, —CF═CF—, —CH═CF—, —CF═CH—, —C≡C— or a single bond, X denotes Cl or F, Y denotes H, Cl, F, alkyl or alkoxy each having 1 to 6 C atoms, t is 0, 1 or 2, and

denote a radical selected from the following groups: a) the group consisting of 1,4-phenylene, 1,4-naphthylene, and 2,6-naphthylene, in which one or two CH groups may be replaced by N and in which one or more H atoms may be replaced by L, b) the group consisting of trans-1,4-cyclohexylene, 1,4-cyclohexenylene, bicyclo[1.1.1]-pentane-1,3-diyl, 4,4′-bicyclohexylene, bicyclo[2.2.2]octane-1,4-diyl or spiro[3.3]heptane-2,6-diyl, in which one or more non-adjacent CH₂ groups may be replaced by —O— and/or —S— and in which one or more H atoms may be replaced by F, c) the group consisting of thiophene-2,5-diyl, thieno[3,2-b]thiophene-2,5-diyl or selenophene-2,5-diyl, each of which may also be mono- or polysubstituted by L, and L on each occurrence, identically or differently, denotes F, Cl, CN, SCN, SF₅ or straight-chain, in each case optionally fluorinated, alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 C atoms or branched, in each case optionally fluorinated, alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 3 to 12 C atoms.
 2. The compound according to claim 1, wherein

independently of one another, denote

wherein

 alternatively denotes

 and L¹ and L² identically or differently, denote F, Cl or straight chain alkyl having 1 to 12 C atoms, straight-chain alkenyl having 2 to 12 C atoms, or branched or cyclic alkyl or alkenyl having 3 to 12 C atoms.
 3. The compound according to claim 1, wherein Z^(C1) and Z^(C2), identically or differently, denote —C≡C— or a single bond.
 4. The compound according to claim 1, selected from compounds of formulae C-1 to C-11

in which L¹, L² and L³ identically or differently, denote H, F, Cl, methyl, ethyl, n-propyl, isopropyl, cyclopropyl, cyclobutyl, cyclopentyl or cyclopentenyl.
 5. The compound according to claim 1, wherein X denotes F.
 6. The compound according to claim 1, wherein R^(C) denotes alkyl having 1 to 12 C atoms.
 7. The compound according to claim 1, wherein the group R^(C) denotes R^(P).
 8. A liquid crystal medium comprising one or more compounds according to claim
 1. 9. The liquid crystal medium according to claim 8, wherein the medium comprises one or more compounds of formulae I, II or III,

in which R¹ denotes H, unfluorinated alkyl or unfluorinated alkoxy having 1 to 17 C atoms, or unfluorinated alkenyl, unfluorinated alkenyloxy or unfluorinated alkoxyalkyl having 2 to 15 C atoms, in which one or more CH₂-groups may be replaced by

n is 0, 1 or 2,

on each occurrence, independently of one another, denote

in which R^(L), on each occurrence identically or differently, denotes H or alkyl having 1 to 6 C atoms, and wherein

 alternatively denotes

R² denotes H, unfluorinated alkyl or unfluorinated alkoxy having 1 to 17 C atoms, or unfluorinated alkenyl, unfluorinated alkenyloxy or unfluorinated alkoxyalkyl having 2 to 15 C atoms, in which one or more CH₂-groups may be replaced by

Z²¹ denotes trans-CH═CH—, trans-CF═CF— or —C≡C—, and

independently of one another, denote

in which R^(L), on each occurrence identically or differently, denotes H or alkyl having 1 to 6 C atoms; R³ denotes H, unfluorinated alkyl or unfluorinated alkoxy having 1 to 17 C atoms, or unfluorinated alkenyl, unfluorinated alkenyloxy or unfluorinated alkoxyalkyl having 2 to 15 C atoms, in which one or more CH₂-groups may be replaced by

one of Z³¹ and Z³², denotes trans-CH═CH—, trans-CF═CF— or —C≡C— and the other one, independently thereof, denotes —C≡C—, trans-CH═CH—, trans-CF═CF— or a single bond, and

independently of one another, denote

in which R^(L), on each occurrence identically or differently, denotes H or alkyl having 1 to 6 C atoms, and wherein

 alternatively denotes


10. The liquid-crystal medium according to claim 9, wherein the medium comprises one or more compounds selected from compounds of formulae I-1 to I-5

in which L¹, L² and L³ on each occurrence, identically or differently, denote H or F, wherein

on each occurrence, independently of one another, denote

in which R^(L), on each occurrence identically or differently, denotes H or alkyl having 1 to 6 C atoms, and wherein

 alternatively denotes


11. The liquid-crystal medium according to claim 9, wherein the medium comprises one or more compounds of formulae II-1 to II-3

wherein

independently of one another, denote

in which R^(L), on each occurrence identically or differently, denotes H or alkyl having 1 to 6 C atoms.
 12. The liquid-crystal medium according to claim 9, wherein the medium comprises one or more compounds of formulae III-1 to III-6

in which Z³¹ and Z³² independently of one another, denote trans-CH═CH— or trans-CF═CF—, and in formula III-6 one of Z³¹ and Z³² alternatively denotes —C≡C—, and wherein

independently of one another, denote

in which R^(L), on each occurrence identically or differently, denotes H or alkyl having 1 to 6 C atoms, and wherein

 alternatively denotes


13. The liquid-crystal medium according to claim 9, wherein the medium comprises one or more compounds of formula T

in which R^(T) denotes halogen, CN, NCS, R^(F), R^(F)—O— or R^(F)—S—, wherein R^(F) denotes fluorinated alkyl having 1 to 12 C atoms or fluorinated alkenyl having 2 to 12 C atoms,

on each occurrence, independently of one another, denote

L⁴ and L⁵ identically or differently, denote F, Cl or straight chain alkyl having 1 to 12 C atoms, straight-chain alkenyl having 2 to 12 C atoms, or branched or cyclic alkyl or alkenyl having 3 to 12 C atoms; Z^(T3), Z^(T4) identically or differently, denote —CH═CH—, —CF═CF—, —CH═CF—, —CF═CH—, —C≡C— or a single bond, and t is 0 or
 1. 14. A component for high-frequency technology, comprising the liquid crystal medium according to claim
 9. 15. The component according to claim 14, wherein the component comprises a liquid-crystal based antenna element, a phase shifter, a tunable filter, a tunable metamaterial structure, a matching network, or a varactor.
 16. A microwave antenna array, comprising one or more components according to claim
 14. 